diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 439395297e1b0..36c5997ea78ac 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -105,17 +105,6 @@
 
     *Justin Talbott*
 
-*   Infer default `:inverse_of` option for `delegated_type` definitions.
-
-    ```ruby
-    class Entry < ApplicationRecord
-      delegated_type :entryable, types: %w[ Message ]
-      # => defaults to inverse_of: :entry
-    end
-    ```
-
-    *Sean Doyle*
-
 *   Add support for `ActiveRecord::Point` type casts using `Hash` values
 
     This allows `ActiveRecord::Point` to be cast or serialized from a hash
diff --git a/activerecord/lib/active_record/delegated_type.rb b/activerecord/lib/active_record/delegated_type.rb
index 44735adc9e096..e680edfa4e2f2 100644
--- a/activerecord/lib/active_record/delegated_type.rb
+++ b/activerecord/lib/active_record/delegated_type.rb
@@ -220,14 +220,6 @@ module DelegatedType
     # [:primary_key]
     #   Specify the method that returns the primary key of associated object used for the convenience methods.
     #   By default this is +id+.
-    # [+:inverse_of+]
-    #   Specifies the name of the #belongs_to association on the associated object
-    #   that is the inverse of this #has_one association. By default, the class
-    #   singularized class name is used unless a <tt>:foreign_key</tt> option is
-    #   also provided. For example, a call to
-    #   <tt>Entry.delegated_type</tt> will default to <tt>inverse_of: :entry</tt>.
-    #   See ActiveRecord::Associations::ClassMethods's overview on Bi-directional
-    #   associations for more detail.
     #
     # Option examples:
     #   class Entry < ApplicationRecord
@@ -237,8 +229,6 @@ module DelegatedType
     #   Entry#message_uuid      # => returns entryable_uuid, when entryable_type == "Message", otherwise nil
     #   Entry#comment_uuid      # => returns entryable_uuid, when entryable_type == "Comment", otherwise nil
     def delegated_type(role, types:, **options)
-      options[:inverse_of] = model_name.singular unless options.key?(:inverse_of) || options.key?(:foreign_key)
-
       belongs_to role, options.delete(:scope), **options.merge(polymorphic: true)
       define_delegated_type_methods role, types: types, options: options
     end
diff --git a/activerecord/test/cases/delegated_type_test.rb b/activerecord/test/cases/delegated_type_test.rb
index 4455cdecb81fc..b541435ee605a 100644
--- a/activerecord/test/cases/delegated_type_test.rb
+++ b/activerecord/test/cases/delegated_type_test.rb
@@ -3,7 +3,6 @@
 require "cases/helper"
 require "models/account"
 require "models/entry"
-require "models/essay"
 require "models/message"
 require "models/recipient"
 require "models/comment"
@@ -12,12 +11,12 @@
 require "models/uuid_comment"
 
 class DelegatedTypeTest < ActiveRecord::TestCase
-  fixtures :comments, :accounts, :essays
+  fixtures :comments, :accounts, :posts
 
   setup do
     @entry_with_message = Entry.create! entryable: Message.new(subject: "Hello world!"), account: accounts(:signals37)
     @entry_with_comment = Entry.create! entryable: comments(:greetings), account: accounts(:signals37)
-    @entry_with_essay = Entry.create! thing: essays(:mary_stay_home), account: accounts(:signals37)
+    @entry_with_post = Entry.create! thing: posts(:welcome), account: accounts(:signals37)
 
     if current_adapter?(:PostgreSQLAdapter)
       @uuid_entry_with_message = UuidEntry.create! uuid: SecureRandom.uuid, entryable: UuidMessage.new(uuid: SecureRandom.uuid, subject: "Hello world!")
@@ -37,7 +36,7 @@ class DelegatedTypeTest < ActiveRecord::TestCase
   test "delegated class with custom foreign_type" do
     assert_equal Message, @entry_with_message.thing_class
     assert_equal Comment, @entry_with_comment.thing_class
-    assert_equal Essay, @entry_with_essay.thing_class
+    assert_equal Post, @entry_with_post.thing_class
   end
 
   test "delegated type name" do
@@ -57,9 +56,9 @@ class DelegatedTypeTest < ActiveRecord::TestCase
   end
 
   test "delegated type predicates with custom foreign_type" do
-    assert_predicate @entry_with_essay, :essay?
-    assert_not @entry_with_message.essay?
-    assert_not @entry_with_comment.essay?
+    assert_predicate @entry_with_post, :post?
+    assert_not @entry_with_message.post?
+    assert_not @entry_with_comment.post?
   end
 
   test "scope" do
@@ -68,7 +67,7 @@ class DelegatedTypeTest < ActiveRecord::TestCase
   end
 
   test "scope with custom foreign_type" do
-    assert_predicate Entry.essays.first, :essay?
+    assert_predicate Entry.posts.first, :post?
   end
 
   test "accessor" do
@@ -97,15 +96,6 @@ class DelegatedTypeTest < ActiveRecord::TestCase
     assert_nil @uuid_entry_with_comment.uuid_message_uuid
   end
 
-  test "association inverse_of" do
-    created = @entry_with_message.message
-    updated = @entry_with_message.build_entryable subject: "Goodbye world!"
-
-    assert_changes -> { @entry_with_message.reload.message }, from: created, to: updated do
-      updated.save!
-    end
-  end
-
   test "touch account" do
     previous_account_updated_at  = @entry_with_message.account.updated_at
     previous_entry_updated_at    = @entry_with_message.updated_at
diff --git a/activerecord/test/models/comment.rb b/activerecord/test/models/comment.rb
index 76b319ac65bae..c8ebc12429069 100644
--- a/activerecord/test/models/comment.rb
+++ b/activerecord/test/models/comment.rb
@@ -1,13 +1,9 @@
 # frozen_string_literal: true
 
-require "models/entryable"
-
 # `counter_cache` requires association class before `attr_readonly`.
 class Post < ActiveRecord::Base; end
 
 class Comment < ActiveRecord::Base
-  include Entryable
-
   scope :limit_by, lambda { |l| limit(l) }
   scope :containing_the_letter_e, -> { where("comments.body LIKE '%e%'") }
   scope :not_again, -> { where("comments.body NOT LIKE '%again%'") }
diff --git a/activerecord/test/models/entry.rb b/activerecord/test/models/entry.rb
index 37f71e6874b74..c5ca4bcc14892 100644
--- a/activerecord/test/models/entry.rb
+++ b/activerecord/test/models/entry.rb
@@ -5,6 +5,6 @@ class Entry < ActiveRecord::Base
   belongs_to :account, touch: true
 
   # alternate delegation for custom foreign_key/foreign_type
-  delegated_type :thing, types: %w[ Essay ],
+  delegated_type :thing, types: %w[ Post ],
     foreign_key: :entryable_id, foreign_type: :entryable_type
 end
diff --git a/activerecord/test/models/entryable.rb b/activerecord/test/models/entryable.rb
deleted file mode 100644
index 7225542acb49f..0000000000000
--- a/activerecord/test/models/entryable.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-# frozen_string_literal: true
-
-require "models/entry"
-
-module Entryable
-  extend ActiveSupport::Concern
-
-  included do
-    has_one :entry, as: :entryable, touch: true
-  end
-end
diff --git a/activerecord/test/models/essay.rb b/activerecord/test/models/essay.rb
index 662fc7fab6d0d..eb2fb51f1f16c 100644
--- a/activerecord/test/models/essay.rb
+++ b/activerecord/test/models/essay.rb
@@ -1,10 +1,6 @@
 # frozen_string_literal: true
 
-require "models/entryable"
-
 class Essay < ActiveRecord::Base
-  include Entryable
-
   belongs_to :author, primary_key: :name
   belongs_to :writer, primary_key: :name, polymorphic: true
   belongs_to :category, primary_key: :name
diff --git a/activerecord/test/models/message.rb b/activerecord/test/models/message.rb
index 67ecb50586ee1..b8a6c315e2a01 100644
--- a/activerecord/test/models/message.rb
+++ b/activerecord/test/models/message.rb
@@ -1,9 +1,6 @@
 # frozen_string_literal: true
 
-require "models/entryable"
-
 class Message < ActiveRecord::Base
-  include Entryable
-
+  has_one  :entry, as: :entryable, touch: true
   has_many :recipients
 end
diff --git a/activerecord/test/models/uuid_comment.rb b/activerecord/test/models/uuid_comment.rb
index bd145178e1cb9..62736af32f63b 100644
--- a/activerecord/test/models/uuid_comment.rb
+++ b/activerecord/test/models/uuid_comment.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "models/uuid_entryable"
-
 class UuidComment < ActiveRecord::Base
-  include UuidEntryable
+  has_one :uuid_entry, as: :entryable
 end
diff --git a/activerecord/test/models/uuid_entryable.rb b/activerecord/test/models/uuid_entryable.rb
deleted file mode 100644
index 4200208979849..0000000000000
--- a/activerecord/test/models/uuid_entryable.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-# frozen_string_literal: true
-
-require "models/uuid_entry"
-
-module UuidEntryable
-  extend ActiveSupport::Concern
-
-  included do
-    has_one :uuid_entry, as: :entryable
-  end
-end
diff --git a/activerecord/test/models/uuid_message.rb b/activerecord/test/models/uuid_message.rb
index 0b69cbaf56d86..904414f8de5cf 100644
--- a/activerecord/test/models/uuid_message.rb
+++ b/activerecord/test/models/uuid_message.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "models/uuid_entryable"
-
 class UuidMessage < ActiveRecord::Base
-  include UuidEntryable
+  has_one :uuid_entry, as: :entryable
 end