diff --git a/plugins/AutoMode/plugin.py b/plugins/AutoMode/plugin.py
index 738aae428..f11ed3238 100644
--- a/plugins/AutoMode/plugin.py
+++ b/plugins/AutoMode/plugin.py
@@ -163,8 +163,9 @@ def unban():
                         # We're not in the channel anymore.
                         pass
                 schedule.addEvent(unban, time.time()+period)
-            banmask =conf.supybot.protocols.irc.banmask.makeBanmask(msg.prefix)
-            irc.queueMsg(ircmsgs.ban(channel, banmask))
+            banmasks = conf.supybot.protocols.irc.banmask.makeExtBanmasks(
+                msg.prefix, channel=channel, network=irc.network)
+            irc.queueMsg(ircmsgs.bans(channel, banmasks))
             irc.queueMsg(ircmsgs.kick(channel, msg.nick))
 
         try:
diff --git a/plugins/Channel/plugin.py b/plugins/Channel/plugin.py
index 1f3f97fed..3589e8bd5 100644
--- a/plugins/Channel/plugin.py
+++ b/plugins/Channel/plugin.py
@@ -321,13 +321,16 @@ def kban(self, irc, msg, args,
         --exact bans only the exact hostmask; --nick bans just the nick;
         --user bans just the user, and --host bans just the host
         You can combine the --nick, --user, and --host options as you choose.
+        If --account is provided and the user is logged in and the network
+        supports account bans, this will ban the user's account instead.
         <channel> is only necessary if the message isn't sent in the channel itself.
         """
         self._ban(irc, msg, args,
                 channel, optlist, bannedNick, expiry, reason, True)
     kban = wrap(kban,
                 ['op',
-                 getopts({'exact':'', 'nick':'', 'user':'', 'host':''}),
+                 getopts({'exact':'', 'nick':'', 'user':'', 'host':'',
+                          'account': ''}),
                  ('haveHalfop+', _('kick or ban someone')),
                  'nickInChannel',
                  optional('expiry', 0),
@@ -343,13 +346,16 @@ def iban(self, irc, msg, args,
         don't specify a number of seconds) it will ban the person indefinitely.
         --exact can be used to specify an exact hostmask.
         You can combine the --nick, --user, and --host options as you choose.
+        If --account is provided and the user is logged in and the network
+        supports account bans, this will ban the user's account instead.
         <channel> is only necessary if the message isn't sent in the channel itself.
         """
         self._ban(irc, msg, args,
                 channel, optlist, bannedNick, expiry, None, False)
     iban = wrap(iban,
                 ['op',
-                 getopts({'exact':'', 'nick':'', 'user':'', 'host':''}),
+                 getopts({'exact':'', 'nick':'', 'user':'', 'host':'',
+                          'account': ''}),
                  ('haveHalfop+', _('ban someone')),
                  first('nick', 'hostmask'),
                  optional('expiry', 0)])
@@ -362,18 +368,22 @@ def _ban(self, irc, msg, args,
             try:
                 bannedHostmask = irc.state.nickToHostmask(target)
                 banmaskstyle = conf.supybot.protocols.irc.banmask
-                banmask = banmaskstyle.makeBanmask(bannedHostmask, [o[0] for o in optlist])
+                banmasks = banmaskstyle.makeExtBanmasks(
+                    bannedHostmask, [o[0] for o in optlist],
+                    channel=channel, network=irc.network)
             except KeyError:
                 if not conf.supybot.protocols.irc.strictRfc() and \
                         target.startswith('$'):
                     # Select the last part, or the whole target:
                     bannedNick = target.split(':')[-1]
-                    banmask = bannedHostmask = target
+                    bannedHostmask = target
+                    banmasks = [bannedHostmask]
                 else:
                     irc.error(format(_('I haven\'t seen %s.'), bannedNick), Raise=True)
         else:
             bannedNick = ircutils.nickFromHostmask(target)
-            banmask = bannedHostmask = target
+            bannedHostmask = target
+            banmasks = [bannedHostmask]
         if not irc.isNick(bannedNick):
             self.log.warning('%q tried to kban a non nick: %q',
                              msg.prefix, bannedNick)
@@ -389,30 +399,47 @@ def _ban(self, irc, msg, args,
         if not reason:
             reason = msg.nick
         capability = ircdb.makeChannelCapability(channel, 'op')
+
         # Check (again) that they're not trying to make us kickban ourself.
-        if ircutils.hostmaskPatternEqual(banmask, irc.prefix):
-            if ircutils.hostmaskPatternEqual(bannedHostmask, irc.prefix):
+        self_account_extban = ircutils.accountExtban(irc, irc.nick)
+        for banmask in banmasks:
+            if ircutils.hostmaskPatternEqual(banmask, irc.prefix):
+                if ircutils.hostmaskPatternEqual(bannedHostmask, irc.prefix):
+                    self.log.warning('%q tried to make me kban myself.',msg.prefix)
+                    irc.error(_('I cowardly refuse to ban myself.'))
+                    return
+                else:
+                    self.log.warning('Using exact hostmask since banmask would '
+                                     'ban myself.')
+                    banmasks = [bannedHostmask]
+            elif self_account_extban is not None \
+                    and banmask.lower() == self_account_extban.lower():
                 self.log.warning('%q tried to make me kban myself.',msg.prefix)
                 irc.error(_('I cowardly refuse to ban myself.'))
                 return
-            else:
-                self.log.warning('Using exact hostmask since banmask would '
-                                 'ban myself.')
-                banmask = bannedHostmask
+
+
         # Now, let's actually get to it.  Check to make sure they have
         # #channel,op and the bannee doesn't have #channel,op; or that the
         # bannee and the banner are both the same person.
         def doBan():
             if irc.state.channels[channel].isOp(bannedNick):
                 irc.queueMsg(ircmsgs.deop(channel, bannedNick))
-            irc.queueMsg(ircmsgs.ban(channel, banmask))
+            irc.queueMsg(ircmsgs.bans(channel, banmasks))
             if kick:
                 irc.queueMsg(ircmsgs.kick(channel, bannedNick, reason))
             if expiry > 0:
                 def f():
-                    if channel in irc.state.channels and \
-                       banmask in irc.state.channels[channel].bans:
-                        irc.queueMsg(ircmsgs.unban(channel, banmask))
+                    if channel not in irc.state.channels:
+                        return
+                    remaining_banmasks = [
+                        banmask
+                        for banmask in banmasks
+                        if banmask in irc.state.channels[channel].bans
+                    ]
+                    if remaining_banmasks:
+                        irc.queueMsg(ircmsgs.unbans(
+                            channel, remaining_banmasks))
                 schedule.addEvent(f, expiry)
         if bannedNick == msg.nick:
             doBan()
@@ -583,7 +610,7 @@ def hostmask(self, irc, msg, args, channel, banmask):
         hostmask = wrap(hostmask, ['op', ('haveHalfop+', _('ban someone')), 'text'])
 
         @internationalizeDocstring
-        def add(self, irc, msg, args, channel, banmask, expires):
+        def add(self, irc, msg, args, channel, banmasks, expires):
             """[<channel>] <nick|hostmask> [<expires>]
 
             If you have the #channel,op capability, this will effect a
@@ -597,10 +624,15 @@ def add(self, irc, msg, args, channel, banmask, expires):
             channel itself.
             """
             c = ircdb.channels.getChannel(channel)
-            c.addBan(banmask, expires)
+            if isinstance(banmasks, str):
+                banmasks = [banmasks]
+            for banmask in banmasks:
+                c.addBan(banmask, expires)
             ircdb.channels.setChannel(channel, c)
             irc.replySuccess()
-        add = wrap(add, ['op', first('hostmask', 'banmask'), additional('expiry', 0)])
+        add = wrap(add, ['op',
+                         first('hostmask', 'extbanmasks'),
+                         additional('expiry', 0)])
 
         @internationalizeDocstring
         def remove(self, irc, msg, args, channel, banmask):
diff --git a/plugins/Channel/test.py b/plugins/Channel/test.py
index 4295ef081..bcfc52786 100644
--- a/plugins/Channel/test.py
+++ b/plugins/Channel/test.py
@@ -161,9 +161,13 @@ def testVoice(self):
         self.assertTrue(m.command == 'MODE' and
                         m.args == (self.channel, '+v', 'bar'))
 
-    def assertKban(self, query, hostmask, **kwargs):
+    def assertKban(self, query, *hostmasks, **kwargs):
         m = self.getMsg(query, **kwargs)
-        self.assertEqual(m, ircmsgs.ban(self.channel, hostmask))
+        self.assertEqual(m.command, "MODE", m)
+        self.assertEqual(m.args[0], self.channel, m)
+        self.assertEqual(m.args[1], "+" + "b" * len(hostmasks), m)
+        self.assertCountEqual(m.args[2:], hostmasks, m)
+
         m = self.getMsg(' ')
         self.assertEqual(m.command, 'KICK')
     def assertBan(self, query, hostmask, **kwargs):
@@ -185,6 +189,30 @@ def testIban(self):
         self.assertBan('iban $a:nyuszika7h', '$a:nyuszika7h')
         self.assertNotError('unban $a:nyuszika7h')
 
+    def testWontIbanItself(self):
+        self.irc.state.supported['ACCOUNTEXTBAN'] = 'a,account'
+        self.irc.state.supported['EXTBAN'] = '~,abc'
+
+        self.irc.feedMsg(ircmsgs.join(self.channel,
+                                      prefix='foobar!user@host.domain.tld'))
+        self.irc.feedMsg(ircmsgs.op(self.channel, self.irc.nick))
+
+        # not authenticated, falls back to hostname and notices the match
+        self.assertError('iban --account ' + self.nick)
+
+        self.irc.feedMsg(ircmsgs.IrcMsg(prefix=self.prefix, command='ACCOUNT',
+                                        args=['botaccount']))
+
+        # notices the matching account
+        self.assertError('iban --account ' + self.nick)
+
+        self.irc.feedMsg(ircmsgs.IrcMsg(prefix='othernick!otheruser@otherhost',
+                                        command='ACCOUNT',
+                                        args=['botaccount']))
+
+        # ditto
+        self.assertError('iban --account othernick')
+
     def testKban(self):
         self.irc.prefix = 'something!else@somehwere.else'
         self.irc.nick = 'something'
@@ -219,11 +247,108 @@ def join():
 
         self.assertRegexp('kban adlkfajsdlfkjsd', 'adlkfajsdlfkjsd is not in')
 
+    def testAccountKbanNoAccount(self):
+        self.irc.prefix = 'something!else@somehwere.else'
+        self.irc.nick = 'something'
+        self.irc.state.supported['ACCOUNTEXTBAN'] = 'a,account'
+        self.irc.state.supported['EXTBAN'] = '~,abc'
+        def join():
+            self.irc.feedMsg(ircmsgs.join(
+                self.channel, prefix='foobar!user@host.domain.tld'))
+        join()
+        self.irc.feedMsg(ircmsgs.op(self.channel, self.irc.nick))
+        self.assertKban('kban --account --exact foobar',
+                        'foobar!user@host.domain.tld')
+        join()
+        self.assertKban('kban --account foobar',
+                        '*!*@host.domain.tld')
+        join()
+        with conf.supybot.protocols.irc.banmask.context(['user', 'host']):
+            # falls back from --account to config
+            self.assertKban('kban --account foobar',
+                            '*!user@host.domain.tld')
+        join()
+        with conf.supybot.protocols.irc.banmask.context(['account']):
+            # falls back from --account to config, then to only the host
+            self.assertKban('kban --account foobar',
+                            '*!*@host.domain.tld')
+        join()
+        self.assertKban('kban --account --host foobar',
+                        '*!*@host.domain.tld')
+
+    def testAccountKbanLoggedOut(self):
+        self.irc.prefix = 'something!else@somehwere.else'
+        self.irc.nick = 'something'
+        self.irc.state.supported['ACCOUNTEXTBAN'] = 'a,account'
+        self.irc.state.supported['EXTBAN'] = '~,abc'
+        self.irc.feedMsg(ircmsgs.IrcMsg(
+            prefix='foobar!user@host.domain.tld',
+            command='ACCOUNT', args=['*']))
+        def join():
+            self.irc.feedMsg(ircmsgs.join(
+                self.channel, prefix='foobar!user@host.domain.tld'))
+        join()
+        self.irc.feedMsg(ircmsgs.op(self.channel, self.irc.nick))
+        self.assertKban('kban --account --exact foobar',
+                        'foobar!user@host.domain.tld')
+        join()
+        self.assertKban('kban --account foobar',
+                        '*!*@host.domain.tld')
+        join()
+        with conf.supybot.protocols.irc.banmask.context(['user', 'host']):
+            # falls back from --account to config
+            self.assertKban('kban --account foobar',
+                            '*!user@host.domain.tld')
+        join()
+        with conf.supybot.protocols.irc.banmask.context(['account']):
+            # falls back from --account to config, then to only the host
+            self.assertKban('kban --account foobar',
+                            '*!*@host.domain.tld')
+        join()
+        self.assertKban('kban --account --host foobar',
+                        '*!*@host.domain.tld')
+
+    def testAccountKbanLoggedIn(self):
+        self.irc.prefix = 'something!else@somehwere.else'
+        self.irc.nick = 'something'
+        self.irc.state.supported['ACCOUNTEXTBAN'] = 'a,account'
+        self.irc.state.supported['EXTBAN'] = '~,abc'
+        self.irc.feedMsg(ircmsgs.IrcMsg(
+            prefix='foobar!user@host.domain.tld',
+            command='ACCOUNT', args=['account1']))
+        def join():
+            self.irc.feedMsg(ircmsgs.join(
+                self.channel, prefix='foobar!user@host.domain.tld'))
+        join()
+        self.irc.feedMsg(ircmsgs.op(self.channel, self.irc.nick))
+
+
+        for style in (['exact'], ['account', 'exact']):
+            with conf.supybot.protocols.irc.banmask.context(style):
+                self.assertKban('kban --account --exact foobar',
+                                '~a:account1', 'foobar!user@host.domain.tld')
+                join()
+                self.assertKban('kban --account foobar',
+                                '~a:account1')
+                join()
+                self.assertKban('kban --account --host foobar',
+                                '~a:account1', '*!*@host.domain.tld')
+                join()
+
+        with conf.supybot.protocols.irc.banmask.context(['account', 'exact']):
+            self.assertKban('kban foobar',
+                            '~a:account1', 'foobar!user@host.domain.tld')
+            join()
+
+        with conf.supybot.protocols.irc.banmask.context(['account', 'host']):
+            self.assertKban('kban foobar',
+                            '~a:account1', '*!*@host.domain.tld')
+            join()
+
     def testBan(self):
         with conf.supybot.protocols.irc.banmask.context(['exact']):
             self.assertNotError('ban add foo!bar@baz')
             self.assertNotError('ban remove foo!bar@baz')
-            orig = conf.supybot.protocols.irc.strictRfc()
             with conf.supybot.protocols.irc.strictRfc.context(True):
                 # something wonky is going on here. irc.error (src/Channel.py|449)
                 # is being called but the assert is failing
@@ -249,7 +374,6 @@ def testBanList(self):
                             '"foobar!*@baz" (never expires)')
 
     def testIgnore(self):
-        orig = conf.supybot.protocols.irc.banmask()
         def ignore(given, expect=None):
             if expect is None:
                 expect = given
@@ -257,8 +381,9 @@ def ignore(given, expect=None):
             self.assertResponse('channel ignore list', "'%s'" % expect)
             self.assertNotError('channel ignore remove %s' % expect)
             self.assertRegexp('channel ignore list', 'not currently')
-        ignore('foo!bar@baz', '*!*@baz')
-        ignore('foo!*@*')
+        with conf.supybot.protocols.irc.banmask.context(['host']):
+            ignore('foo!bar@baz', '*!*@baz')
+            ignore('foo!*@*')
         with conf.supybot.protocols.irc.banmask.context(['exact']):
             ignore('foo!bar@baz')
             ignore('foo!*@*')
diff --git a/src/commands.py b/src/commands.py
index f93e7ce47..7da905fa4 100644
--- a/src/commands.py
+++ b/src/commands.py
@@ -435,7 +435,14 @@ def getBanmask(irc, msg, args, state):
     getChannel(irc, msg, args, state)
     banmaskstyle = conf.supybot.protocols.irc.banmask
     state.args[-1] = banmaskstyle.makeBanmask(state.args[-1],
-            channel=state.channel)
+            channel=state.channel, network=irc.network)
+
+def getExtBanmasks(irc, msg, args, state):
+    getHostmask(irc, msg, args, state)
+    getChannel(irc, msg, args, state)
+    banmaskstyle = conf.supybot.protocols.irc.extbanmask
+    state.args[-1] = banmaskstyle.makeExtBanmasks(state.args[-1],
+            channel=state.channel, network=irc.network)
 
 def getUser(irc, msg, args, state):
     try:
@@ -806,6 +813,7 @@ def getText(irc, msg, args, state):
     'commandName': getCommandName,
     'email': getEmail,
     'expiry': getExpiry,
+    'extbanmasks': getExtBanmasks,
     'filename': getSomething, # XXX Check for validity.
     'float': getFloat,
     'glob': getGlob,
diff --git a/src/conf.py b/src/conf.py
index 0544613ab..f090816b3 100644
--- a/src/conf.py
+++ b/src/conf.py
@@ -1191,7 +1191,7 @@ def isNick(s, strictRfc=None, **kw):
 
 class Banmask(registry.SpaceSeparatedSetOfStrings):
     __slots__ = ('__parent', '__dict__') # __dict__ is needed to set __doc__
-    validStrings = ('exact', 'nick', 'user', 'host')
+    validStrings = ('exact', 'nick', 'user', 'host', 'account')
     def __init__(self, *args, **kwargs):
         assert self.validStrings, 'There must be some valid strings.  ' \
                                   'This is a bug.'
@@ -1225,13 +1225,43 @@ def makeBanmask(self, hostmask, options=None, channel=None, network=None):
         isn't specified via options, the value of
         conf.supybot.protocols.irc.banmask is used.
 
+        Unlike :meth:`makeExtBanmasks`, this is guaranteed to return an
+        RFC1459-like mask, suitable for ircdb's ignore lists.
+
         options - A list specifying which parts of the hostmask should
         explicitly be matched: nick, user, host.  If 'exact' is given, then
-        only the exact hostmask will be used."""
-        if not channel:
-            channel = dynamic.channel
+        only the exact hostmask will be used.
+        """
         if not network:
             network = dynamic.irc.network
+        if not options:
+            options = supybot.protocols.irc.banmask.getSpecific(
+                network, channel)()
+        options = [option for option in options if option != 'account']
+        masks = self.makeExtBanmasks(
+            hostmask, options, channel, network=network)
+        assert len(masks) == 1, 'Unexpected number of banmasks: %r' % masks
+        return masks[0]
+
+    def makeExtBanmasks(self, hostmask, options=None, channel=None, *, network):
+        """Create banmasks from the given hostmask.  If a style of banmask
+        isn't specified via options, the value of
+        conf.supybot.protocols.irc.banmask is used.
+
+        Depending on the options and configuration, this may return a mask
+        in the format of an extban (eg. "~account:foobar" on UnrealIRCd).
+        If this is unwanted (eg. to pass to ircdb's ignore lists), use
+        :meth:`makeBanmask` instead.
+
+        options - A list specifying which parts of the hostmask should
+        explicitly be matched: nick, user, host.  If 'exact' is given, then
+        only the exact hostmask will be used.
+        If 'account' is given (and not after 'exact') and the user is
+        logged in and the server supports account extbans, then an account
+        extban is returned instead.
+        """
+        if not channel:
+            channel = dynamic.channel
         (nick, user, host) = ircutils.splitHostmask(hostmask)
         bnick = '*'
         buser = '*'
@@ -1239,19 +1269,62 @@ def makeBanmask(self, hostmask, options=None, channel=None, network=None):
         if not options:
             options = supybot.protocols.irc.banmask.getSpecific(
                 network, channel)()
+
+        add_star_mask = False
+        masks = []
+
         for option in options:
             if option == 'nick':
                 bnick = nick
+                add_star_mask = True
             elif option == 'user':
                 buser = user
+                add_star_mask = True
             elif option == 'host':
                 bhost = host
+                add_star_mask = True
             elif option == 'exact':
-                return hostmask
+                masks.append(hostmask)
+            elif option == 'account':
+                import supybot.world as world
+                irc = world.getIrc(network)
+                if irc is None:
+                    continue
+                extban = ircutils.accountExtban(irc, nick)
+                if extban is not None:
+                    masks.append(extban)
+            else:
+                from . import log
+                log.warning(
+                    "Unknown mask option passed to makeExtBanmasks: %r",
+                    option)
+
+        if add_star_mask and (bnick, buser, bhost) != ('*', '*', '*'):
+            masks.append(ircutils.joinHostmask(bnick, buser, bhost))
+
         if (bnick, buser, bhost) == ('*', '*', '*') and \
-                ircutils.isUserHostmask(hostmask):
-            return hostmask
-        return ircutils.joinHostmask(bnick, buser, bhost)
+                options == ['account'] and \
+                not masks:
+            # found no ban mask to set (because options == ['account'] and user
+            # is logged out?), try again with the default ban mask
+            options = supybot.protocols.irc.banmask.getSpecific(
+                    network, channel)()
+            options = [option for option in options if option != 'account']
+            return self.makeExtBanmasks(
+                hostmask, options=options, channel=channel, network=network)
+
+        if (bnick, buser, bhost) == ('*', '*', '*') and \
+                ircutils.isUserHostmask(hostmask) and \
+                not masks:
+            # still no ban mask found, fallback to the host, if any
+            if host != '*':
+                masks.append(ircutils.joinHostmask('*', '*', host))
+            else:
+                # if no host, fall back to the exact mask provided
+                masks.append(hostmask)
+
+        return masks
+
 
 registerChannelValue(supybot.protocols.irc, 'banmask',
     Banmask(['host'], _("""Determines what will be used as the
diff --git a/src/irclib.py b/src/irclib.py
index 233f86f97..b4cfe677e 100644
--- a/src/irclib.py
+++ b/src/irclib.py
@@ -681,6 +681,13 @@ class IrcState(IrcCommandDispatcher, log.Firewalled):
         Stores the last hostmask of a seen nick.
 
         :type: ircutils.IrcDict[str, str]
+
+    .. attribute:: nicksToAccounts
+
+        Stores the current services account name of a seen nick (or
+        :const:`None` for un-identified nicks)
+
+        :type: ircutils.IrcDict[str, Optional[str]]
     """
     __firewalled__ = {'addMsg': None}
 
@@ -689,7 +696,8 @@ def __init__(self, history=None, supported=None,
                  nicksToHostmasks=None, channels=None,
                  capabilities_req=None,
                  capabilities_ack=None, capabilities_nak=None,
-                 capabilities_ls=None):
+                 capabilities_ls=None,
+                 nicksToAccounts=None):
         self.fsm = IrcStateFsm()
         if history is None:
             history = RingBuffer(conf.supybot.protocols.irc.maxHistoryLength())
@@ -697,6 +705,8 @@ def __init__(self, history=None, supported=None,
             supported = utils.InsensitivePreservingDict()
         if nicksToHostmasks is None:
             nicksToHostmasks = ircutils.IrcDict()
+        if nicksToAccounts is None:
+            nicksToAccounts = ircutils.IrcDict()
         if channels is None:
             channels = ircutils.IrcDict()
         self.capabilities_req = capabilities_req or set()
@@ -708,6 +718,7 @@ def __init__(self, history=None, supported=None,
         self.history = history
         self.channels = channels
         self.nicksToHostmasks = nicksToHostmasks
+        self.nicksToAccounts = nicksToAccounts
 
         # Batches usually finish and are way shorter than 3600s, but
         # we need to:
@@ -725,6 +736,7 @@ def reset(self):
         self.channels.clear()
         self.supported.clear()
         self.nicksToHostmasks.clear()
+        self.nicksToAccounts.clear()
         self.capabilities_req = set()
         self.capabilities_ack = set()
         self.capabilities_nak = set()
@@ -745,13 +757,16 @@ def reset(self):
 
     def __reduce__(self):
         return (self.__class__, (self.history, self.supported,
-                                 self.nicksToHostmasks, self.channels))
+                                 self.nicksToHostmasks,
+                                 self.nicksToAccounts,
+                                 self.channels))
 
     def __eq__(self, other):
         return self.history == other.history and \
                self.channels == other.channels and \
                self.supported == other.supported and \
                self.nicksToHostmasks == other.nicksToHostmasks and \
+               self.nicksToAccounts == other.nicksToAccounts and \
                self.batches == other.batches
 
     def __ne__(self, other):
@@ -761,6 +776,7 @@ def copy(self):
         ret = self.__class__()
         ret.history = copy.deepcopy(self.history)
         ret.nicksToHostmasks = copy.deepcopy(self.nicksToHostmasks)
+        ret.nicksToAccounts = copy.deepcopy(self.nicksToAccounts)
         ret.channels = copy.deepcopy(self.channels)
         ret.batches = copy.deepcopy(self.batches)
         return ret
@@ -770,6 +786,8 @@ def addMsg(self, irc, msg):
         self.history.append(msg)
         if ircutils.isUserHostmask(msg.prefix) and not msg.command == 'NICK':
             self.nicksToHostmasks[msg.nick] = msg.prefix
+        if 'account' in msg.server_tags:
+            self.nicksToAccounts[msg.nick] = msg.server_tags['account']
         if 'batch' in msg.server_tags:
             batch_name = msg.server_tags['batch']
             assert batch_name in self.batches, \
@@ -788,6 +806,12 @@ def nickToHostmask(self, nick):
         """Returns the hostmask for a given nick."""
         return self.nicksToHostmasks[nick]
 
+    def nickToAccount(self, nick):
+        """Returns the account for a given nick, or None if the nick is logged
+        out. Raises :exc:`KeyError` if the nick was not seen or its account is
+        not known yet."""
+        return self.nicksToAccounts[nick]
+
     def getParentBatches(self, msg):
         """Given an IrcMsg, returns a list of all batches that contain it,
         innermost first.
@@ -957,6 +981,11 @@ def do354(self, irc, msg):
         (n, t, user, ip, host, nick, status, account, gecos) = msg.args
         hostmask = '%s!%s@%s' % (nick, user, host)
         self.nicksToHostmasks[nick] = hostmask
+        if account == '0':
+            # logged out
+            self.nicksToAccounts[nick] = None
+        else:
+            self.nicksToAccounts[nick] = account
 
     def do353(self, irc, msg):
         # NAMES reply.
@@ -978,6 +1007,7 @@ def do353(self, irc, msg):
             stripped_item = item.lstrip(prefix_chars)
             item_prefix = item[0:-len(stripped_item)]
             if ircutils.isUserHostmask(stripped_item):
+                # https://ircv3.net/specs/extensions/userhost-in-names
                 nick = ircutils.nickFromHostmask(stripped_item)
                 self.nicksToHostmasks[nick] = stripped_item
                 name = item_prefix + nick
@@ -989,11 +1019,20 @@ def do353(self, irc, msg):
             c.modes['s'] = None
 
     def doChghost(self, irc, msg):
+        # https://ircv3.net/specs/extensions/chghost
         (user, host) = msg.args
         nick = msg.nick
         hostmask = '%s!%s@%s' % (nick, user, host)
         self.nicksToHostmasks[nick] = hostmask
 
+    def doAccount(self, irc, msg):
+        # https://ircv3.net/specs/extensions/account-notify
+        account = msg.args[0]
+        if account == '*':
+            self.nicksToAccounts[msg.nick] = None
+        else:
+            self.nicksToAccounts[msg.nick] = account
+
     def doJoin(self, irc, msg):
         for channel in msg.args[0].split(','):
             if channel in self.channels:
@@ -1004,6 +1043,12 @@ def doJoin(self, irc, msg):
                 self.channels[channel] = chan
                 # I don't know why this assert was here.
                 #assert msg.nick == irc.nick, msg
+        if 'extended-join' in self.capabilities_ack:
+            account = msg.args[1]
+            if account == '*':
+                self.nicksToAccounts[msg.nick] = None
+            else:
+                self.nicksToAccounts[msg.nick] = account
 
     def do367(self, irc, msg):
         # Example:
@@ -1083,6 +1128,8 @@ def doQuit(self, irc, msg):
         if msg.nick in self.nicksToHostmasks:
             # If we're quitting, it may not be.
             del self.nicksToHostmasks[msg.nick]
+        if msg.nick in self.nicksToAccounts:
+            del self.nicksToAccounts[msg.nick]
 
     def doTopic(self, irc, msg):
         if len(msg.args) == 1:
@@ -1100,6 +1147,7 @@ def do332(self, irc, msg):
     def doNick(self, irc, msg):
         newNick = msg.args[0]
         oldNick = msg.nick
+
         try:
             if msg.user and msg.host:
                 # Nick messages being handed out from the bot itself won't
@@ -1109,6 +1157,13 @@ def doNick(self, irc, msg):
             del self.nicksToHostmasks[oldNick]
         except KeyError:
             pass
+
+        try:
+            self.nicksToAccounts[newNick] = self.nicksToAccounts[oldNick]
+            del self.nicksToAccounts[oldNick]
+        except KeyError:
+            pass
+
         channel_names = ircutils.IrcSet()
         for (name, channel) in self.channels.items():
             if msg.nick in channel.users:
diff --git a/src/ircutils.py b/src/ircutils.py
index 035ba9a13..4f3a93bea 100644
--- a/src/ircutils.py
+++ b/src/ircutils.py
@@ -345,6 +345,25 @@ def banmask(hostmask):
         else:
             return '*!*@'  + host
 
+
+def accountExtban(irc, nick):
+    """If 'nick' is logged in and the network supports account extbans,
+    returns a ban mask for it. If not, returns None."""
+    if 'ACCOUNTEXTBAN' not in irc.state.supported:
+        return None
+    if 'EXTBAN' not in irc.state.supported:
+        return None
+    try:
+        account = irc.state.nickToAccount(nick)
+    except KeyError:
+        account = None
+    if account is None:
+        return None
+    account_extban = irc.state.supported['ACCOUNTEXTBAN'].split(',')[0]
+    extban_prefix = irc.state.supported['EXTBAN'].split(',', 1)[0]
+    return '%s%s:%s'% (extban_prefix, account_extban, account)
+
+
 _plusRequireArguments = 'ovhblkqeI'
 _minusRequireArguments = 'ovhbkqeI'
 def separateModes(args):
diff --git a/src/test.py b/src/test.py
index 08e43ba07..5fa48028b 100644
--- a/src/test.py
+++ b/src/test.py
@@ -318,7 +318,8 @@ def assertError(self, query, **kwargs):
             raise TimeoutError(query)
         if lastGetHelp not in m.args[1]:
             self.assertTrue(m.args[1].startswith('Error:'),
-                            '%r did not error: %s' % (query, m.args[1]))
+                            '%r did not error: %s' %
+                            (query, ' '.join(m.args[1:])))
         return m
 
     def assertSnarfError(self, query, **kwargs):
diff --git a/test/test_irclib.py b/test/test_irclib.py
index 91cc5faf6..6f4f560f7 100644
--- a/test/test_irclib.py
+++ b/test/test_irclib.py
@@ -579,6 +579,112 @@ def testChghost(self):
             command='CHGHOST', args=['bar2', 'baz2']))
         self.assertEqual(st.nickToHostmask('foo'), 'foo!bar2@baz2')
 
+    def testNickToAccountBaseJoin(self):
+        st = irclib.IrcState()
+
+        st.addMsg(self.irc, ircmsgs.join('#foo', prefix='foo!bar@baz'))
+        st.addMsg(self.irc, ircmsgs.join('#foo', prefix='bar!baz@qux'))
+        with self.assertRaises(KeyError):
+            st.nickToAccount('foo')
+        with self.assertRaises(KeyError):
+            st.nickToAccount('bar')
+
+
+    def testNickToAccountExtendedJoin(self):
+        st = irclib.IrcState()
+        st.capabilities_ack.add('extended-join')
+
+        st.addMsg(self.irc, ircmsgs.IrcMsg(
+            command='JOIN', prefix='foo!bar@baz',
+            args=['#foo', 'account1', 'real name1']))
+        st.addMsg(self.irc, ircmsgs.IrcMsg(
+            command='JOIN', prefix='bar!baz@qux',
+            args=['#foo', 'account2', 'real name2']))
+        st.addMsg(self.irc, ircmsgs.IrcMsg(
+            command='JOIN', prefix='baz!qux@quux',
+            args=['#foo', '*', 'real name3']))
+        self.assertEqual(st.nickToAccount('foo'), 'account1')
+        self.assertEqual(st.nickToAccount('bar'), 'account2')
+        self.assertIsNone(st.nickToAccount('baz'))
+        with self.assertRaises(KeyError):
+            st.nickToAccount('qux')
+
+        # QUIT erases the entry
+        with self.subTest("QUIT"):
+            st2 = st.copy()
+            st2.addMsg(self.irc, ircmsgs.quit(prefix='foo!bar@baz'))
+            with self.assertRaises(KeyError):
+                st2.nickToAccount('foo')
+            self.assertEqual(st2.nickToAccount('bar'), 'account2')
+
+            # check st isn't affected by changes to st2
+            self.assertEqual(st.nickToAccount('foo'), 'account1')
+            self.assertEqual(st.nickToAccount('bar'), 'account2')
+
+        # NICK moves the entry
+        with self.subTest("NICK"):
+            st2 = st.copy()
+            st2.addMsg(self.irc, ircmsgs.IrcMsg(prefix='foo!bar@baz',
+                                                command='NICK', args=['foo2']))
+            with self.assertRaises(KeyError):
+                st2.nickToAccount('foo')
+            self.assertEqual(st2.nickToAccount('foo2'), 'account1')
+            self.assertEqual(st2.nickToAccount('bar'), 'account2')
+
+            # check st isn't affected by changes to st2
+            self.assertEqual(st.nickToAccount('foo'), 'account1')
+            self.assertEqual(st.nickToAccount('bar'), 'account2')
+
+        # NICK moves the entry (and overwrites if needed)
+        with self.subTest("NICK with overwrite"):
+            st2 = st.copy()
+            st2.addMsg(self.irc, ircmsgs.IrcMsg(prefix='foo!bar@baz',
+                                                command='NICK', args=['bar']))
+            with self.assertRaises(KeyError):
+                st2.nickToAccount('foo')
+            self.assertEqual(st2.nickToAccount('bar'), 'account1')
+
+            # check st isn't affected by changes to st2
+            self.assertEqual(st.nickToAccount('foo'), 'account1')
+            self.assertEqual(st.nickToAccount('bar'), 'account2')
+
+    def testNickToAccountWho(self):
+        st = irclib.IrcState()
+
+        st.addMsg(self.irc, ircmsgs.IrcMsg(command='352', # RPL_WHOREPLY
+            args=[self.irc.nick, '#chan', 'bar', 'baz', 'server.example',
+                  'foo', 'H', '0 real name']))
+        with self.assertRaises(KeyError):
+            st.nickToAccount('foo')
+
+    def testNickToAccountWhox(self):
+        st = irclib.IrcState()
+
+        st.addMsg(self.irc, ircmsgs.IrcMsg(command='354', # RPL_WHOSPCRPL
+            args=[self.irc.nick, '1', 'bar', '127.0.0.1', 'baz',
+                  'foo', 'H', 'account1', 'real name']))
+        self.assertEqual(st.nickToAccount('foo'), 'account1')
+
+        st.addMsg(self.irc, ircmsgs.IrcMsg(command='354', # RPL_WHOSPCRPL
+            args=[self.irc.nick, '1', 'bar', '127.0.0.1', 'baz',
+                  'foo', 'H', '0', 'real name']))
+        self.assertIsNone(st.nickToAccount('foo'))
+
+    def testAccountNotify(self):
+        st = irclib.IrcState()
+
+        st.addMsg(self.irc, ircmsgs.IrcMsg(prefix='foo!bar@baz',
+            command='ACCOUNT', args=['account1']))
+        self.assertEqual(st.nickToAccount('foo'), 'account1')
+
+        st.addMsg(self.irc, ircmsgs.IrcMsg(prefix='foo!bar@baz',
+            command='ACCOUNT', args=['account2']))
+        self.assertEqual(st.nickToAccount('foo'), 'account2')
+
+        st.addMsg(self.irc, ircmsgs.IrcMsg(prefix='foo!bar@baz',
+            command='ACCOUNT', args=['*']))
+        self.assertIsNone(st.nickToAccount('foo'))
+
     def testEq(self):
         state1 = irclib.IrcState()
         state2 = irclib.IrcState()
diff --git a/test/test_ircutils.py b/test/test_ircutils.py
index cb62358c8..59363e73f 100644
--- a/test/test_ircutils.py
+++ b/test/test_ircutils.py
@@ -367,6 +367,60 @@ def testBanmask(self):
                          '*!*@*.host.tld')
         self.assertEqual(ircutils.banmask('foo!bar@2001::'), '*!*@2001::*')
 
+    def testAccountExtban(self):
+        irc = getTestIrc()
+        irc.state.addMsg(irc, ircmsgs.IrcMsg(
+            prefix='foo!bar@baz', command='ACCOUNT', args=['account1']))
+        irc.state.addMsg(irc, ircmsgs.IrcMsg(
+            prefix='bar!baz@qux', command='ACCOUNT', args=['*']))
+
+        with self.subTest('spec example'):
+            irc.state.supported['ACCOUNTEXTBAN'] = 'a,account'
+            irc.state.supported['EXTBAN'] = '~,abc'
+            self.assertEqual(ircutils.accountExtban(irc, 'foo'),
+                             '~a:account1')
+            self.assertIsNone(ircutils.accountExtban(irc, 'bar'))
+            self.assertIsNone(ircutils.accountExtban(irc, 'baz'))
+
+        with self.subTest('InspIRCd'):
+            irc.state.supported['ACCOUNTEXTBAN'] = 'account,R'
+            irc.state.supported['EXTBAN'] = ',abcR'
+            self.assertEqual(ircutils.accountExtban(irc, 'foo'),
+                             'account:account1')
+            self.assertIsNone(ircutils.accountExtban(irc, 'bar'))
+            self.assertIsNone(ircutils.accountExtban(irc, 'baz'))
+
+        with self.subTest('Solanum'):
+            irc.state.supported['ACCOUNTEXTBAN'] = 'a'
+            irc.state.supported['EXTBAN'] = '$,abc'
+            self.assertEqual(ircutils.accountExtban(irc, 'foo'),
+                             '$a:account1')
+            self.assertIsNone(ircutils.accountExtban(irc, 'bar'))
+            self.assertIsNone(ircutils.accountExtban(irc, 'baz'))
+
+        with self.subTest('UnrealIRCd'):
+            irc.state.supported['ACCOUNTEXTBAN'] = 'account,a'
+            irc.state.supported['EXTBAN'] = '~,abc'
+            self.assertEqual(ircutils.accountExtban(irc, 'foo'),
+                             '~account:account1')
+            self.assertIsNone(ircutils.accountExtban(irc, 'bar'))
+            self.assertIsNone(ircutils.accountExtban(irc, 'baz'))
+
+        with self.subTest('no ACCOUNTEXTBAN'):
+            irc.state.supported.pop('ACCOUNTEXTBAN')
+            irc.state.supported['EXTBAN'] = '~,abc'
+            self.assertIsNone(ircutils.accountExtban(irc, 'foo'))
+            self.assertIsNone(ircutils.accountExtban(irc, 'bar'))
+            self.assertIsNone(ircutils.accountExtban(irc, 'baz'))
+
+        with self.subTest('no EXTBAN'):
+            irc.state.supported['ACCOUNTEXTBAN'] = 'account,a'
+            irc.state.supported.pop('EXTBAN')
+            self.assertIsNone(ircutils.accountExtban(irc, 'foo'))
+            self.assertIsNone(ircutils.accountExtban(irc, 'bar'))
+            self.assertIsNone(ircutils.accountExtban(irc, 'baz'))
+
+
     def testSeparateModes(self):
         self.assertEqual(ircutils.separateModes(['+ooo', 'x', 'y', 'z']),
                          [('+o', 'x'), ('+o', 'y'), ('+o', 'z')])