diff --git a/activesupport/lib/active_support/cache/file_store.rb b/activesupport/lib/active_support/cache/file_store.rb
index 2ab632a3a5..4af4909741 100644
--- a/activesupport/lib/active_support/cache/file_store.rb
+++ b/activesupport/lib/active_support/cache/file_store.rb
@@ -1,6 +1,5 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/marshal"
 require "active_support/core_ext/file/atomic"
 require "active_support/core_ext/string/conversions"
 require "uri/common"
diff --git a/activesupport/lib/active_support/cache/mem_cache_store.rb b/activesupport/lib/active_support/cache/mem_cache_store.rb
index f3482881b9..68b080ab3b 100644
--- a/activesupport/lib/active_support/cache/mem_cache_store.rb
+++ b/activesupport/lib/active_support/cache/mem_cache_store.rb
@@ -8,7 +8,6 @@ rescue LoadError => e
 end
 
 require "active_support/core_ext/enumerable"
-require "active_support/core_ext/marshal"
 require "active_support/core_ext/array/extract_options"
 
 module ActiveSupport
diff --git a/activesupport/lib/active_support/cache/redis_cache_store.rb b/activesupport/lib/active_support/cache/redis_cache_store.rb
index 065b81eca3..41153ea577 100644
--- a/activesupport/lib/active_support/cache/redis_cache_store.rb
+++ b/activesupport/lib/active_support/cache/redis_cache_store.rb
@@ -16,7 +16,6 @@ rescue LoadError
 end
 
 require "active_support/digest"
-require "active_support/core_ext/marshal"
 
 module ActiveSupport
   module Cache
diff --git a/activesupport/lib/active_support/core_ext/marshal.rb b/activesupport/lib/active_support/core_ext/marshal.rb
deleted file mode 100644
index 5ff0e34d82..0000000000
--- a/activesupport/lib/active_support/core_ext/marshal.rb
+++ /dev/null
@@ -1,26 +0,0 @@
-# frozen_string_literal: true
-
-require "active_support/core_ext/string/inflections"
-
-module ActiveSupport
-  module MarshalWithAutoloading # :nodoc:
-    def load(source, proc = nil)
-      super(source, proc)
-    rescue ArgumentError, NameError => exc
-      if exc.message.match(%r|undefined class/module (.+?)(?:::)?\z|)
-        # try loading the class/module
-        loaded = $1.constantize
-
-        raise unless $1 == loaded.name
-
-        # if it is an IO we need to go back to read the object
-        source.rewind if source.respond_to?(:rewind)
-        retry
-      else
-        raise exc
-      end
-    end
-  end
-end
-
-Marshal.singleton_class.prepend(ActiveSupport::MarshalWithAutoloading)
diff --git a/activesupport/test/cache/behaviors.rb b/activesupport/test/cache/behaviors.rb
index db51dd69ab..5c40b4bf2b 100644
--- a/activesupport/test/cache/behaviors.rb
+++ b/activesupport/test/cache/behaviors.rb
@@ -1,6 +1,5 @@
 # frozen_string_literal: true
 
-require_relative "behaviors/autoloading_cache_behavior"
 require_relative "behaviors/cache_delete_matched_behavior"
 require_relative "behaviors/cache_increment_decrement_behavior"
 require_relative "behaviors/cache_instrumentation_behavior"
diff --git a/activesupport/test/cache/behaviors/autoloading_cache_behavior.rb b/activesupport/test/cache/behaviors/autoloading_cache_behavior.rb
deleted file mode 100644
index 25e3550c02..0000000000
--- a/activesupport/test/cache/behaviors/autoloading_cache_behavior.rb
+++ /dev/null
@@ -1,43 +0,0 @@
-# frozen_string_literal: true
-
-require_relative "../../dependencies_test_helpers"
-
-module AutoloadingCacheBehavior
-  include DependenciesTestHelpers
-
-  def test_simple_autoloading
-    with_autoloading_fixtures do
-      @cache.write("foo", EM.new)
-    end
-
-    remove_constants(:EM)
-    ActiveSupport::Dependencies.clear
-
-    with_autoloading_fixtures do
-      assert_kind_of EM, @cache.read("foo")
-    end
-
-    remove_constants(:EM)
-    ActiveSupport::Dependencies.clear
-  end
-
-  def test_two_classes_autoloading
-    with_autoloading_fixtures do
-      @cache.write("foo", [EM.new, ClassFolder.new])
-    end
-
-    remove_constants(:EM, :ClassFolder)
-    ActiveSupport::Dependencies.clear
-
-    with_autoloading_fixtures do
-      loaded = @cache.read("foo")
-      assert_kind_of Array, loaded
-      assert_equal 2, loaded.size
-      assert_kind_of EM, loaded[0]
-      assert_kind_of ClassFolder, loaded[1]
-    end
-
-    remove_constants(:EM, :ClassFolder)
-    ActiveSupport::Dependencies.clear
-  end
-end
diff --git a/activesupport/test/cache/stores/file_store_test.rb b/activesupport/test/cache/stores/file_store_test.rb
index 308c34a959..b43de1b5de 100644
--- a/activesupport/test/cache/stores/file_store_test.rb
+++ b/activesupport/test/cache/stores/file_store_test.rb
@@ -36,7 +36,6 @@ class FileStoreTest < ActiveSupport::TestCase
   include CacheDeleteMatchedBehavior
   include CacheIncrementDecrementBehavior
   include CacheInstrumentationBehavior
-  include AutoloadingCacheBehavior
 
   def test_clear
     gitkeep = File.join(cache_dir, ".gitkeep")
diff --git a/activesupport/test/cache/stores/mem_cache_store_test.rb b/activesupport/test/cache/stores/mem_cache_store_test.rb
index 867d40f262..f65fbcf85d 100644
--- a/activesupport/test/cache/stores/mem_cache_store_test.rb
+++ b/activesupport/test/cache/stores/mem_cache_store_test.rb
@@ -55,7 +55,6 @@ class MemCacheStoreTest < ActiveSupport::TestCase
   include CacheIncrementDecrementBehavior
   include CacheInstrumentationBehavior
   include EncodedKeyCacheBehavior
-  include AutoloadingCacheBehavior
   include ConnectionPoolBehavior
   include FailureSafetyBehavior
 
diff --git a/activesupport/test/cache/stores/redis_cache_store_test.rb b/activesupport/test/cache/stores/redis_cache_store_test.rb
index 9fc4341f54..334ece1862 100644
--- a/activesupport/test/cache/stores/redis_cache_store_test.rb
+++ b/activesupport/test/cache/stores/redis_cache_store_test.rb
@@ -136,7 +136,6 @@ module ActiveSupport::Cache::RedisCacheStoreTests
     include LocalCacheBehavior
     include CacheIncrementDecrementBehavior
     include CacheInstrumentationBehavior
-    include AutoloadingCacheBehavior
     include EncodedKeyCacheBehavior
 
     def test_fetch_multi_uses_redis_mget
diff --git a/activesupport/test/core_ext/marshal_test.rb b/activesupport/test/core_ext/marshal_test.rb
deleted file mode 100644
index 5e72518651..0000000000
--- a/activesupport/test/core_ext/marshal_test.rb
+++ /dev/null
@@ -1,165 +0,0 @@
-# frozen_string_literal: true
-
-require_relative "../abstract_unit"
-require "active_support/core_ext/marshal"
-require_relative "../dependencies_test_helpers"
-
-class MarshalTest < ActiveSupport::TestCase
-  include ActiveSupport::Testing::Isolation
-  include DependenciesTestHelpers
-
-  def teardown
-    ActiveSupport::Dependencies.clear
-    remove_constants(:EM, :ClassFolder)
-  end
-
-  test "that Marshal#load still works" do
-    sanity_data = ["test", [1, 2, 3], { a: [1, 2, 3] }, ActiveSupport::TestCase]
-    sanity_data.each do |obj|
-      dumped = Marshal.dump(obj)
-      assert_equal Marshal.method(:load).super_method.call(dumped), Marshal.load(dumped)
-    end
-  end
-
-  test "that Marshal#load still works when passed a proc" do
-    example_string = "test"
-
-    example_proc = Proc.new do |o|
-      if o.is_a?(String)
-        o.capitalize!
-      end
-    end
-
-    dumped = Marshal.dump(example_string)
-    assert_equal Marshal.load(dumped, example_proc), "Test"
-  end
-
-  test "that a missing class is autoloaded from string" do
-    dumped = nil
-    with_autoloading_fixtures do
-      dumped = Marshal.dump(EM.new)
-    end
-
-    remove_constants(:EM)
-    ActiveSupport::Dependencies.clear
-
-    with_autoloading_fixtures do
-      object = nil
-      assert_nothing_raised do
-        object = Marshal.load(dumped)
-      end
-
-      assert_kind_of EM, object
-    end
-  end
-
-  test "that classes in sub modules work" do
-    dumped = nil
-    with_autoloading_fixtures do
-      dumped = Marshal.dump(ClassFolder::ClassFolderSubclass.new)
-    end
-
-    remove_constants(:ClassFolder)
-    ActiveSupport::Dependencies.clear
-
-    with_autoloading_fixtures do
-      object = nil
-      assert_nothing_raised do
-        object = Marshal.load(dumped)
-      end
-
-      assert_kind_of ClassFolder::ClassFolderSubclass, object
-    end
-  end
-
-  test "that more than one missing class is autoloaded" do
-    dumped = nil
-    with_autoloading_fixtures do
-      dumped = Marshal.dump([EM.new, ClassFolder.new])
-    end
-
-    remove_constants(:EM, :ClassFolder)
-    ActiveSupport::Dependencies.clear
-
-    with_autoloading_fixtures do
-      loaded = Marshal.load(dumped)
-      assert_equal 2, loaded.size
-      assert_kind_of EM, loaded[0]
-      assert_kind_of ClassFolder, loaded[1]
-    end
-  end
-
-  test "when one constant resolves to another" do
-    class Parent; C = Class.new; end
-    class Child < Parent; C = Class.new; end
-
-    dump = Marshal.dump(Child::C.new)
-
-    Child.send(:remove_const, :C)
-
-    assert_raise(ArgumentError) { Marshal.load(dump) }
-  end
-
-  test "that a real missing class is causing an exception" do
-    dumped = nil
-    with_autoloading_fixtures do
-      dumped = Marshal.dump(EM.new)
-    end
-
-    remove_constants(:EM)
-    ActiveSupport::Dependencies.clear
-
-    assert_raise(NameError) do
-      Marshal.load(dumped)
-    end
-  end
-
-  test "when first class is autoloaded and second not" do
-    dumped = nil
-    class SomeClass
-    end
-
-    with_autoloading_fixtures do
-      dumped = Marshal.dump([EM.new, SomeClass.new])
-    end
-
-    remove_constants(:EM)
-    self.class.send(:remove_const, :SomeClass)
-    ActiveSupport::Dependencies.clear
-
-    with_autoloading_fixtures do
-      assert_raise(NameError) do
-        Marshal.load(dumped)
-      end
-
-      assert_nothing_raised do
-        EM.new
-      end
-
-      assert_raise(NameError, "We expected SomeClass to not be loaded but it is!") do
-        SomeClass.new
-      end
-    end
-  end
-
-  test "loading classes from files trigger autoloading" do
-    Tempfile.open("object_serializer_test") do |f|
-      with_autoloading_fixtures do
-        Marshal.dump(EM.new, f)
-      end
-
-      f.rewind
-      remove_constants(:EM)
-      ActiveSupport::Dependencies.clear
-
-      with_autoloading_fixtures do
-        object = nil
-        assert_nothing_raised do
-          object = Marshal.load(f)
-        end
-
-        assert_kind_of EM, object
-      end
-    end
-  end
-end
diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md
index 94c5e00b07..41c9959705 100644
--- a/guides/source/active_support_core_extensions.md
+++ b/guides/source/active_support_core_extensions.md
@@ -4000,25 +4000,6 @@ NOTE: Defined in `active_support/core_ext/file/atomic.rb`.
 
 [File.atomic_write]: https://api.rubyonrails.org/classes/File.html#method-c-atomic_write
 
-Extensions to `Marshal`
------------------------
-
-### `load`
-
-Active Support adds constant autoloading support to `load`.
-
-For example, the file cache store deserializes this way:
-
-```ruby
-File.open(file_name) { |f| Marshal.load(f) }
-```
-
-If the cached data refers to a constant that is unknown at that point, the autoloading mechanism is triggered and if it succeeds the deserialization is retried transparently.
-
-WARNING. If the argument is an `IO` it needs to respond to `rewind` to be able to retry. Regular files respond to `rewind`.
-
-NOTE: Defined in `active_support/core_ext/marshal.rb`.
-
 Extensions to `NameError`
 -------------------------