diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 4372e9f139636..f5da038de649e 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,10 @@
+*   SQLite3Adapter: Ensure fork-safety.
+
+    Previously, forking a Rails process with open SQLite3 database connections could result in
+    database file corruption under certain circumstances.
+
+    *Mike Dalessio*
+
 *   Add support for PostgreSQL `IF NOT EXISTS` via the `:if_not_exists` option
     on the `add_enum_value` method.
 
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
index 68af021a06122..8735689b4eea6 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
@@ -442,6 +442,16 @@ def disconnect(raise_on_acquisition_timeout = true)
         end
       end
 
+      # Notify connections that a fork is imminent, to allow them to take necessary measures to
+      # ensure fork-safety.
+      #
+      # See AbstractAdapter#prepare_to_fork!
+      def prepare_to_fork! # :nodoc:
+        @connections.each do |conn|
+          conn.prepare_to_fork!
+        end
+      end
+
       # Disconnects all connections in the pool, and clears the pool.
       #
       # The pool first tries to gain ownership of all connections. If unable to
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index df1a2656b5db0..427ebf09b2f8b 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -696,6 +696,13 @@ def reconnect!(restore_transactions: false)
         end
       end
 
+      # Prepare the connection for an imminent fork. Some database adapters are not fork-safe
+      # (specifically sqlite3), and so this gives the adapter an opportunity to close or finalize
+      # any objects that the child process should not inherit.
+      def prepare_to_fork!
+        # This should be overridden by concrete adapters.
+      end
+
       # Disconnects from the database if already connected. Otherwise, this
       # method does nothing.
       def disconnect!
diff --git a/activerecord/lib/active_record/connection_adapters/pool_config.rb b/activerecord/lib/active_record/connection_adapters/pool_config.rb
index 0010a48acd225..1db570fb32135 100644
--- a/activerecord/lib/active_record/connection_adapters/pool_config.rb
+++ b/activerecord/lib/active_record/connection_adapters/pool_config.rb
@@ -17,6 +17,10 @@ def schema_reflection
       private_constant :INSTANCES
 
       class << self
+        def prepare_to_fork!
+          INSTANCES.each_key(&:prepare_to_fork!)
+        end
+
         def discard_pools!
           INSTANCES.each_key(&:discard_pool!)
         end
@@ -66,6 +70,14 @@ def pool
         @pool || synchronize { @pool ||= ConnectionAdapters::ConnectionPool.new(self) }
       end
 
+      def prepare_to_fork!
+        synchronize do
+          return unless @pool
+
+          @pool.prepare_to_fork!
+        end
+      end
+
       def discard_pool!
         return unless @pool
 
@@ -80,4 +92,5 @@ def discard_pool!
   end
 end
 
+ActiveSupport::ForkTracker.before_fork { ActiveRecord::ConnectionAdapters::PoolConfig.prepare_to_fork! }
 ActiveSupport::ForkTracker.after_fork { ActiveRecord::ConnectionAdapters::PoolConfig.discard_pools! }
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index 888741ba262c4..d73b0ee40155e 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -497,6 +497,19 @@ def initialize_type_map(m)
       TYPE_MAP = Type::TypeMap.new.tap { |m| initialize_type_map(m) }
       EXTENDED_TYPE_MAPS = Concurrent::Map.new
 
+      def prepare_to_fork!
+        # It's not safe to fork with an open sqlite connection, because when the object is GCed in
+        # the child process, it can interfere with existing or subsequent connections to the
+        # database in the child process, which can lead to corruption.
+        #
+        # Note that closing the database will raise a BusyException unless all related statements
+        # are also closed, which the AbstractAdapter's disconnect! method handles for us.
+        #
+        # More on sqlite fork-safety: https://www.sqlite.org/howtocorrupt.html section 2.6
+        # More on Rails db corruption: https://github.com/rails/solid_queue/issues/324
+        disconnect!
+      end
+
       private
         # See https://www.sqlite.org/limits.html,
         # the default value is 999 when not configured.