diff --git a/CHANGES.rst b/CHANGES.rst
index 61d4f862..a0a5d5d6 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -8,15 +8,23 @@ Version 5.5.0
 
 Released TBD
 
-Features
-++++++++
+Features & Improvements
++++++++++++++++++++++++
 - (:issue:`956`) Add support for changing registered user's email (:py:data:`SECURITY_CHANGE_EMAIL`).
+- (:pr:`xxx`) Change default password hash to argon2 (was bcrypt). See below for details.
 
 Fixes
 +++++
 - (:pr:`972`) Set :py:data:`SECURITY_CSRF_COOKIE` at beginning (GET /login) of authentication
   ritual - just as we return the CSRF token. (thanks @e-goto)
 
+Backwards Compatibility Concerns
++++++++++++++++++++++++++++++++++
+- Notes around the change to argon2 as the default password hash:
+    - applications should add the argon2_cffi package to their requirements (it is included in the flask_security[common] extras).
+    - leave bcrypt installed to that old passwords still work.
+    - the default configuration will re-hash passwords with argon2 upon first use.
+
 Version 5.4.3
 -------------
 
diff --git a/README.rst b/README.rst
index 5d5e5dd7..da73bc30 100644
--- a/README.rst
+++ b/README.rst
@@ -56,7 +56,7 @@ Goals
     * WebAuthn support (5.0)
     * Two-Factor recovery codes (5.0)
     * First-class support for username as identity (4.1)
-    * Support for fresheness decorator to ensure sensitive operations have new authentication (4.0)
+    * Support for freshness decorator to ensure sensitive operations have new authentication (4.0)
     * Support for email normalization and validation (4.0)
     * Unified signin (username, phone, passwordless) feature (3.4)
 
diff --git a/docs/configuration.rst b/docs/configuration.rst
index ee020978..d4438bc3 100644
--- a/docs/configuration.rst
+++ b/docs/configuration.rst
@@ -80,10 +80,10 @@ These configuration keys are used globally across all features.
 .. py:data:: SECURITY_PASSWORD_HASH
 
     Specifies the password hash algorithm to use when hashing passwords.
-    Recommended values for production systems are ``bcrypt``, ``argon2``, ``sha512_crypt``, or
+    Recommended values for production systems are ``argon2``, ``bcrypt``, or
     ``pbkdf2_sha512``. Some algorithms require the installation  of a backend package (e.g. `bcrypt`_, `argon2`_).
 
-    Default: ``"bcrypt"``.
+    Default: ``"argon2"``.
 
 .. py:data:: SECURITY_PASSWORD_SCHEMES
 
@@ -134,9 +134,11 @@ These configuration keys are used globally across all features.
 
 .. py:data:: SECURITY_PASSWORD_HASH_PASSLIB_OPTIONS
 
-    Pass additional options to the various hashing methods. This is a
-    dict of the form ``{<scheme>__<option>: <value>, ..}``
-    e.g. {"argon2__rounds": 10}.
+    Pass additional options through ``passlib`` to the various hashing methods.
+    This is a dict of the form ``{<scheme>__<option>: <value>, ..}``
+    e.g. {"argon2__time_cost": 3}.
+
+    Default: ``{}``
 
     .. versionadded:: 3.3.1
 
diff --git a/docs/features.rst b/docs/features.rst
index 7e303f5f..4d307465 100644
--- a/docs/features.rst
+++ b/docs/features.rst
@@ -40,12 +40,19 @@ control (such as per-object), you can refer to the Flask-Principal `documentatio
 Password Hashing
 ----------------
 
-Password hashing is enabled with `passlib`_. Passwords are hashed with the
-`bcrypt`_ function by default but you can easily configure the hashing
-algorithm. You should **always use a hashing algorithm** in your production
-environment. Hash algorithms not listed in ``SECURITY_PASSWORD_SINGLE_HASH``
+Password hashing is implemented using `passlib`_. Passwords are hashed with the
+`argon2`_ function by default but you can easily configure other hashing
+algorithms.
+For any given hashing algorithm, consult its documentation on what
+options/values are recommended. For argon2, the `argon2_cffi`_ package
+keeps its default options up to date with `RFC9106`_, and should be suitable for most
+applications. The `OWASP Password Storage Cheat Sheet <owasp_pass_cheat>`_ also
+has a lot of useful suggestions.
+
+You should **always use a hashing algorithm** in your production
+environment. Hash algorithms not listed in :data:`SECURITY_PASSWORD_SINGLE_HASH`
 will be double hashed - first an HMAC will be computed, then the selected hash
-function will be used. In this case - you must provide a ``SECURITY_PASSWORD_SALT``.
+function will be used. In this case - you must provide a :data:`SECURITY_PASSWORD_SALT`.
 A good way to generate this is::
 
     secrets.SystemRandom().getrandbits(128)
@@ -308,6 +315,10 @@ in the `examples` directory.
 .. _documentation on this topic: http://packages.python.org/Flask-Principal/#granular-resource-protection
 .. _passlib: https://passlib.readthedocs.io/en/stable/
 .. _totp secret: https://passlib.readthedocs.io/en/stable/narr/totp-tutorial.html#overview
+.. _argon2: https://en.wikipedia.org/wiki/Argon2
+.. _argon2_cffi: https://pypi.org/project/argon2-cffi/
+.. _RFC9106: https://www.rfc-editor.org/rfc/rfc9106.html
+.. _owasp_pass_cheat: https://cheatsheetseries.owasp.org/cheatsheets/Password_Storage_Cheat_Sheet.html
 .. _bcrypt: https://en.wikipedia.org/wiki/Bcrypt
 .. _PyQRCode: https://pypi.python.org/pypi/PyQRCode/
 .. _Wikipedia: https://en.wikipedia.org/wiki/Multi-factor_authentication
diff --git a/docs/installation.rst b/docs/installation.rst
index 280e0a6b..c543239d 100644
--- a/docs/installation.rst
+++ b/docs/installation.rst
@@ -28,7 +28,7 @@ Supported extras are:
 
 * ``babel`` - Translation services. It will install babel and Flask-Babel.
 * ``fsqla`` - Use flask-sqlalchemy and sqlalchemy as your storage interface.
-* ``common`` - Install Flask-Mailman, bcrypt (the default password hash), and bleach.
+* ``common`` - Install Flask-Mailman, argon2 (the default password hash), and bleach.
 * ``mfa`` - Install packages used for multi-factor (two-factor, unified signin, WebAuthn):
   cryptography, qrcode, phonenumberslite (note that for SMS you still need
   to pick an SMS provider and install appropriate packages), and webauthn.
diff --git a/docs/quickstart.rst b/docs/quickstart.rst
index 706f5c83..587874a4 100644
--- a/docs/quickstart.rst
+++ b/docs/quickstart.rst
@@ -13,8 +13,8 @@ There are some complete (but simple) examples available in the *examples* direct
     for some missing packages.
 
 .. note::
-    The default :data:`SECURITY_PASSWORD_HASH` is "bcrypt" - so be sure to install bcrypt.
-    If you opt for a different hash e.g. "argon2" you will need to install the appropriate package e.g. `argon_cffi`_.
+    The default :data:`SECURITY_PASSWORD_HASH` is "argon2" - so be sure to install `argon_cffi`_.
+    If you opt for a different hash e.g. "bcrypt" you will need to install the appropriate package.
 .. danger::
    The examples below place secrets in source files. Never do this for your application
    especially if your source code is placed in a public repo. How you pass in secrets
@@ -67,8 +67,7 @@ possible using Flask-SQLAlchemy and the built-in model mixins:
 
     # Generate a nice key using secrets.token_urlsafe()
     app.config['SECRET_KEY'] = os.environ.get("SECRET_KEY", 'pf9Wkove4IKEAXvy-cQkeDPhv9Cb3Ag-wyJILbq_dFw')
-    # Bcrypt is set as default SECURITY_PASSWORD_HASH, which requires a salt
-    # Generate a good salt using: secrets.SystemRandom().getrandbits(128)
+    # Generate a good salt for password hashing using: secrets.SystemRandom().getrandbits(128)
     app.config['SECURITY_PASSWORD_SALT'] = os.environ.get("SECURITY_PASSWORD_SALT", '146585145368132386173505678016728509634')
 
     # have session and remember cookie be samesite (flask/flask_login)
@@ -167,8 +166,7 @@ and models.py.
 
     # Generate a nice key using secrets.token_urlsafe()
     app.config['SECRET_KEY'] = os.environ.get("SECRET_KEY", 'pf9Wkove4IKEAXvy-cQkeDPhv9Cb3Ag-wyJILbq_dFw')
-    # Bcrypt is set as default SECURITY_PASSWORD_HASH, which requires a salt
-    # Generate a good salt using: secrets.SystemRandom().getrandbits(128)
+    # Generate a good salt for password hashing using: secrets.SystemRandom().getrandbits(128)
     app.config['SECURITY_PASSWORD_SALT'] = os.environ.get("SECURITY_PASSWORD_SALT", '146585145368132386173505678016728509634')
     # Don't worry if email has findable domain
     app.config["SECURITY_EMAIL_VALIDATOR_ARGS"] = {"check_deliverability": False}
@@ -321,8 +319,7 @@ local MongoDB instance):
 
     # Generate a nice key using secrets.token_urlsafe()
     app.config['SECRET_KEY'] = os.environ.get("SECRET_KEY", 'pf9Wkove4IKEAXvy-cQkeDPhv9Cb3Ag-wyJILbq_dFw')
-    # Bcrypt is set as default SECURITY_PASSWORD_HASH, which requires a salt
-    # Generate a good salt using: secrets.SystemRandom().getrandbits(128)
+    # Generate a good salt for password hashing using: secrets.SystemRandom().getrandbits(128)
     app.config['SECURITY_PASSWORD_SALT'] = os.environ.get("SECURITY_PASSWORD_SALT", '146585145368132386173505678016728509634')
     # Don't worry if email has findable domain
     app.config["SECURITY_EMAIL_VALIDATOR_ARGS"] = {"check_deliverability": False}
@@ -413,8 +410,7 @@ possible using Peewee:
 
     # Generate a nice key using secrets.token_urlsafe()
     app.config['SECRET_KEY'] = os.environ.get("SECRET_KEY", 'pf9Wkove4IKEAXvy-cQkeDPhv9Cb3Ag-wyJILbq_dFw')
-    # Bcrypt is set as default SECURITY_PASSWORD_HASH, which requires a salt
-    # Generate a good salt using: secrets.SystemRandom().getrandbits(128)
+    # Generate a good salt for password hashing using: secrets.SystemRandom().getrandbits(128)
     app.config['SECURITY_PASSWORD_SALT'] = os.environ.get("SECURITY_PASSWORD_SALT", '146585145368132386173505678016728509634')
 
     app.config['DATABASE'] = {
diff --git a/docs/two_factor_configurations.rst b/docs/two_factor_configurations.rst
index bed0bcdc..d7dcaa8f 100644
--- a/docs/two_factor_configurations.rst
+++ b/docs/two_factor_configurations.rst
@@ -45,8 +45,7 @@ possible using SQLAlchemy:
     app.config['DEBUG'] = True
     # Generate a nice key using secrets.token_urlsafe()
     app.config['SECRET_KEY'] = os.environ.get("SECRET_KEY", 'pf9Wkove4IKEAXvy-cQkeDPhv9Cb3Ag-wyJILbq_dFw')
-    # Bcrypt is set as default SECURITY_PASSWORD_HASH, which requires a salt
-    # Generate a good salt using: secrets.SystemRandom().getrandbits(128)
+    # Generate a good salt for password hashing using: secrets.SystemRandom().getrandbits(128)
     app.config['SECURITY_PASSWORD_SALT'] = os.environ.get("SECURITY_PASSWORD_SALT", '146585145368132386173505678016728509634')
 
     app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite://'
diff --git a/flask_security/core.py b/flask_security/core.py
index 15567aea..bfd5e402 100644
--- a/flask_security/core.py
+++ b/flask_security/core.py
@@ -135,7 +135,7 @@
     "I18N_DOMAIN": "flask_security",
     "I18N_DIRNAME": "builtin",
     "EMAIL_VALIDATOR_ARGS": None,
-    "PASSWORD_HASH": "bcrypt",
+    "PASSWORD_HASH": "argon2",
     "PASSWORD_SALT": None,
     "PASSWORD_SINGLE_HASH": {
         "django_argon2",
@@ -160,9 +160,8 @@
         "plaintext",
     ],
     "PASSWORD_HASH_OPTIONS": {},  # Deprecated at passlib 1.7
-    "PASSWORD_HASH_PASSLIB_OPTIONS": {
-        "argon2__rounds": 10  # 1.7.1 default is 2.
-    },  # >= 1.7.1 method to pass options.
+    "PASSWORD_HASH_PASSLIB_OPTIONS": {},  # passlib >= 1.7.1 method to pass options
+    # (as part of CryptoContext.using)
     "PASSWORD_LENGTH_MIN": 8,
     "PASSWORD_COMPLEXITY_CHECKER": None,
     "PASSWORD_CHECK_BREACHED": False,
diff --git a/pyproject.toml b/pyproject.toml
index 87d78166..9c5a3a2a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -55,7 +55,7 @@ dependencies = [
 [project.optional-dependencies]
 babel = ["babel>=2.12.1", "flask_babel>=3.1.0"]
 fsqla = ["flask_sqlalchemy>=3.0.3", "sqlalchemy>=2.0.12", "sqlalchemy-utils>=0.41.1"]
-common = ["bcrypt>=4.0.1", "flask_mailman>=0.3.0", "bleach>=6.0.0"]
+common = ["argon2_cffi>=21.3.0", "bcrypt>=4.0.1", "flask_mailman>=0.3.0", "bleach>=6.0.0"]
 mfa = ["cryptography>=40.0.2", "qrcode>=7.4.2", "phonenumberslite>=8.13.11", "webauthn>=2.0.0"]
 low = [
     # Lowest supported versions
diff --git a/tests/test_hashing.py b/tests/test_hashing.py
index b21acd69..abbabbb4 100644
--- a/tests/test_hashing.py
+++ b/tests/test_hashing.py
@@ -3,6 +3,9 @@
     ~~~~~~~~~~~~
 
     hashing tests
+
+    :copyright: (c) 2019-2024 by J. Christopher Wagner (jwag).
+    :license: MIT, see LICENSE for more details.
 """
 
 import timeit
@@ -15,26 +18,33 @@
 from flask_security.utils import hash_password, verify_password, get_hmac
 
 
-def test_verify_password_bcrypt_double_hash(app, sqlalchemy_datastore):
+def test_verify_password_double_hash(app, sqlalchemy_datastore):
     init_app_with_options(
         app,
         sqlalchemy_datastore,
         **{
-            "SECURITY_PASSWORD_HASH": "bcrypt",
+            "SECURITY_PASSWORD_HASH": "argon2",
+            "SECURITY_PASSWORD_HASH_PASSLIB_OPTIONS": {"argon2__rounds": 1},
             "SECURITY_PASSWORD_SALT": "salty",
             "SECURITY_PASSWORD_SINGLE_HASH": False,
         },
     )
     with app.app_context():
-        assert verify_password("pass", hash_password("pass"))
+        hashed_pwd = hash_password("pass")
+        assert verify_password("pass", hashed_pwd)
+        assert "t=1" in hashed_pwd
 
+        # Verify double hash
+        assert verify_password("pass", argon2.hash(get_hmac("pass")))
 
-def test_verify_password_bcrypt_single_hash(app, sqlalchemy_datastore):
+
+def test_verify_password_single_hash(app, sqlalchemy_datastore):
     init_app_with_options(
         app,
         sqlalchemy_datastore,
         **{
-            "SECURITY_PASSWORD_HASH": "bcrypt",
+            "SECURITY_PASSWORD_HASH": "argon2",
+            "SECURITY_PASSWORD_HASH_PASSLIB_OPTIONS": {"argon2__rounds": 1},
             "SECURITY_PASSWORD_SALT": None,
             "SECURITY_PASSWORD_SINGLE_HASH": True,
         },
@@ -48,11 +58,12 @@ def test_verify_password_single_hash_list(app, sqlalchemy_datastore):
         app,
         sqlalchemy_datastore,
         **{
-            "SECURITY_PASSWORD_HASH": "bcrypt",
+            "SECURITY_PASSWORD_HASH": "argon2",
+            "SECURITY_PASSWORD_HASH_PASSLIB_OPTIONS": {"argon2__rounds": 1},
             "SECURITY_PASSWORD_SALT": "salty",
             "SECURITY_PASSWORD_SINGLE_HASH": ["django_pbkdf2_sha256", "plaintext"],
             "SECURITY_PASSWORD_SCHEMES": [
-                "bcrypt",
+                "argon2",
                 "pbkdf2_sha256",
                 "django_pbkdf2_sha256",
                 "plaintext",
@@ -73,9 +84,10 @@ def test_verify_password_backward_compatibility(app, sqlalchemy_datastore):
         app,
         sqlalchemy_datastore,
         **{
-            "SECURITY_PASSWORD_HASH": "bcrypt",
+            "SECURITY_PASSWORD_HASH": "argon2",
+            "SECURITY_PASSWORD_HASH_PASSLIB_OPTIONS": {"argon2__rounds": 1},
             "SECURITY_PASSWORD_SINGLE_HASH": False,
-            "SECURITY_PASSWORD_SCHEMES": ["bcrypt", "plaintext"],
+            "SECURITY_PASSWORD_SCHEMES": ["argon2", "plaintext"],
         },
     )
     with app.app_context():
@@ -85,26 +97,15 @@ def test_verify_password_backward_compatibility(app, sqlalchemy_datastore):
         assert verify_password("pass", plaintext.hash("pass"))
 
 
-def test_verify_password_bcrypt_rounds_too_low(app, sqlalchemy_datastore):
-    with raises(ValueError) as exc_msg:
-        init_app_with_options(
-            app,
-            sqlalchemy_datastore,
-            **{
-                "SECURITY_PASSWORD_HASH": "bcrypt",
-                "SECURITY_PASSWORD_SALT": "salty",
-                "SECURITY_PASSWORD_HASH_OPTIONS": {"bcrypt": {"rounds": 3}},
-            },
-        )
-    assert all(s in str(exc_msg.value) for s in ["rounds", "too low"])
-
-
 def test_login_with_bcrypt_enabled(app, sqlalchemy_datastore):
     init_app_with_options(
         app,
         sqlalchemy_datastore,
         **{
             "SECURITY_PASSWORD_HASH": "bcrypt",
+            "SECURITY_PASSWORD_HASH_PASSLIB_OPTIONS": {
+                "bcrypt__rounds": 4,  # minimum so test is faster
+            },
             "SECURITY_PASSWORD_SALT": "salty",
             "SECURITY_PASSWORD_SINGLE_HASH": False,
         },
@@ -119,28 +120,13 @@ def test_missing_hash_salt_option(app, sqlalchemy_datastore):
             app,
             sqlalchemy_datastore,
             **{
-                "SECURITY_PASSWORD_HASH": "bcrypt",
+                "SECURITY_PASSWORD_HASH": "argon2",
                 "SECURITY_PASSWORD_SALT": None,
                 "SECURITY_PASSWORD_SINGLE_HASH": False,
             },
         )
 
 
-def test_verify_password_argon2(app, sqlalchemy_datastore):
-    init_app_with_options(
-        app,
-        sqlalchemy_datastore,
-        **{"SECURITY_PASSWORD_HASH": "argon2", "SECURITY_PASSWORD_SINGLE_HASH": False},
-    )
-    with app.app_context():
-        hashed_pwd = hash_password("pass")
-        assert verify_password("pass", hashed_pwd)
-        assert "t=10" in hashed_pwd
-
-        # Verify double hash
-        assert verify_password("pass", argon2.hash(get_hmac("pass")))
-
-
 def test_verify_password_argon2_opts(app, sqlalchemy_datastore):
     init_app_with_options(
         app,
@@ -148,7 +134,7 @@ def test_verify_password_argon2_opts(app, sqlalchemy_datastore):
         **{
             "SECURITY_PASSWORD_HASH": "argon2",
             "SECURITY_PASSWORD_HASH_PASSLIB_OPTIONS": {
-                "argon2__rounds": 4,
+                "argon2__rounds": 1,
                 "argon2__salt_size": 16,
                 "argon2__hash_len": 16,
             },
@@ -156,7 +142,7 @@ def test_verify_password_argon2_opts(app, sqlalchemy_datastore):
     )
     with app.app_context():
         hashed_pwd = hash_password("pass")
-        assert "t=4" in hashed_pwd
+        assert "t=1" in hashed_pwd
         assert verify_password("pass", hashed_pwd)
 
 
diff --git a/tests/test_misc.py b/tests/test_misc.py
index a8148ec3..69d29759 100644
--- a/tests/test_misc.py
+++ b/tests/test_misc.py
@@ -292,11 +292,11 @@ def test_change_hash_type(app, sqlalchemy_datastore):
         **{
             "SECURITY_PASSWORD_HASH": "plaintext",
             "SECURITY_PASSWORD_SALT": None,
-            "SECURITY_PASSWORD_SCHEMES": ["bcrypt", "plaintext"],
+            "SECURITY_PASSWORD_SCHEMES": ["argon2", "plaintext"],
         },
     )
 
-    app.config["SECURITY_PASSWORD_HASH"] = "bcrypt"
+    app.config["SECURITY_PASSWORD_HASH"] = "argon2"
     app.config["SECURITY_PASSWORD_SALT"] = "salty"
 
     app.security = Security(