diff --git a/lib/rdoc/parser/ruby.rb b/lib/rdoc/parser/ruby.rb
index ab0544e0b4..d79e72cfee 100644
--- a/lib/rdoc/parser/ruby.rb
+++ b/lib/rdoc/parser/ruby.rb
@@ -133,9 +133,13 @@ class Ruby < Parser
       # Matches an RBS inline type annotation line: #: followed by whitespace
       RBS_SIG_LINE = /\A#:\s/ # :nodoc:
 
-      attr_accessor :visibility
+      attr_writer :visibility
       attr_reader :container, :singleton, :in_proc_block
 
+      def visibility
+        @visibility == :module_function ? :private : @visibility
+      end
+
       def initialize(top_level, content, options, stats)
         super
 
@@ -414,7 +418,7 @@ def handle_meta_method_comment(comment, directives, node)
         handle_code_object_directives(@container, directives)
         is_call_node = node.is_a?(Prism::CallNode)
         singleton_method = false
-        visibility = @visibility
+        visibility = self.visibility
         attributes = rw = line_no = method_name = nil
         directives.each do |directive, (param, line)|
           case directive
@@ -589,24 +593,22 @@ def change_method_to_module_function(names)
         # changes but the singleton method copies must not be documented
         return if document_suppressed?
 
-        new_methods = []
-        @container.methods_matching(names) do |m|
-          s_m = m.dup
-          record_location(s_m)
-          s_m.singleton = true
-          new_methods << s_m
-        end
-        new_methods.each do |method|
-          method.visibility = :public
-          case method
-          when AnyMethod
-            @container.add_method(method)
-          when Attr
-            @container.add_attribute(method)
-          end
-        end
+        @container.methods_matching(names) { |method| add_module_function_copy(method) }
       end
 
+    private def add_module_function_copy(method) # :nodoc:
+      method = method.dup
+      record_location(method)
+      method.singleton = true
+      method.visibility = :public
+      case method
+      when AnyMethod
+        @container.add_method(method)
+      when Attr
+        @container.add_attribute(method)
+      end
+    end
+
       def handle_code_object_directives(code_object, directives) # :nodoc:
         directives.each do |directive, (param)|
           # startdoc/stopdoc/enddoc are handled by apply_document_control_directive.
@@ -718,6 +720,7 @@ def add_method(method_name, receiver_name:, receiver_fallback_type:, visibility:
       end
 
     private def internal_add_method(method_name, container, comment:, directives:, modifier_comment_lines: nil, line_no:, visibility:, singleton:, params:, calls_super:, block_params:, node_id:, type_signature_lines: nil) # :nodoc:
+      module_function = @visibility == :module_function && !singleton && container.equal?(@container)
       meth = AnyMethod.new(method_name, singleton: singleton)
       meth.comment = comment
       handle_code_object_directives(meth, directives) if directives
@@ -743,7 +746,7 @@ def add_method(method_name, receiver_name:, receiver_fallback_type:, visibility:
       meth.type_signature_lines = type_signature_lines
       # An instance method `initialize` is documented as `::new` unless the
       # :notnew: directive is given
-      if method_name == 'initialize' && !singleton
+      if method_name == 'initialize' && !singleton && !module_function
         if meth.dont_rename_initialize
           meth.visibility = :protected
         else
@@ -757,6 +760,8 @@ def add_method(method_name, receiver_name:, receiver_fallback_type:, visibility:
       container.add_method(meth)
       token_stream_loader = @colorizer_context.token_stream_loader(node_id) if node_id
       meth.start_collecting_tokens(:ruby, loader: token_stream_loader)
+
+      add_module_function_copy(meth) if module_function
     end
 
       # Find or create module or class from a given module name using Ruby lexical
@@ -1277,8 +1282,12 @@ def _visit_call_require(call_node)
 
         def _visit_call_module_function(call_node)
           return if @scanner.in_proc_block || @scanner.singleton
-          names = visibility_method_arguments(call_node, singleton: false)&.map(&:to_s)
-          @scanner.change_method_to_module_function(names) if names
+          if call_node.arguments.nil?
+            @scanner.visibility = :module_function
+          else
+            names = visibility_method_arguments(call_node, singleton: false)&.map(&:to_s)
+            @scanner.change_method_to_module_function(names) if names
+          end
         end
 
         def _visit_call_public_private_class_method(call_node, visibility)
diff --git a/test/rdoc/parser/ruby_test.rb b/test/rdoc/parser/ruby_test.rb
index 4ac663abb4..660aeae3d9 100644
--- a/test/rdoc/parser/ruby_test.rb
+++ b/test/rdoc/parser/ruby_test.rb
@@ -1403,6 +1403,176 @@ def m3; end
     assert_equal [:public, :public, :public], singleton_methods.map(&:visibility)
   end
 
+  def test_module_function_without_arguments
+    util_parser <<~RUBY
+      module JSON
+        def before; end
+        module_function
+
+        # :call-seq:
+        #   JSON.parse(source, opts = {}) -> object
+        #
+        # Parses a source.
+        def parse(source, opts = {}); end
+        def generate(object); end
+      end
+    RUBY
+    mod = @store.find_module_named 'JSON'
+    singleton_methods, instance_methods = mod.method_list.partition(&:singleton)
+
+    assert_equal ['before', 'parse', 'generate'], instance_methods.map(&:name)
+    assert_equal [:public, :private, :private], instance_methods.map(&:visibility)
+    assert_equal ['parse', 'generate'], singleton_methods.map(&:name)
+    assert_equal [:public, :public], singleton_methods.map(&:visibility)
+
+    parse = mod.find_method('parse', false)
+    singleton_parse = mod.find_method('parse', true)
+    assert_not_same parse, singleton_parse
+    assert_equal '(source, opts = {})', singleton_parse.params
+    assert_equal 'Parses a source.', singleton_parse.comment.text.strip
+    assert_equal 'JSON.parse(source, opts = {}) -> object', singleton_parse.call_seq
+    assert_equal 'JSON::parse', singleton_parse.full_name
+    assert_equal 'method-c-parse', singleton_parse.aref
+    assert_equal parse.token_stream, singleton_parse.token_stream
+  end
+
+  def test_module_function_without_arguments_reset_by_visibility
+    util_parser <<~RUBY
+      module M
+        module_function
+        def first; end
+        public
+        def pub; end
+        module_function
+        def second; end
+        private
+        def pri; end
+        module_function
+        def third; end
+        protected
+        def pro; end
+      end
+    RUBY
+    mod = @store.find_module_named 'M'
+    instance_methods = mod.method_list.reject(&:singleton)
+
+    assert_equal ['first', 'pub', 'second', 'pri', 'third', 'pro'], instance_methods.map(&:name)
+    assert_equal [:private, :public, :private, :private, :private, :protected], instance_methods.map(&:visibility)
+    assert_equal ['first', 'second', 'third'], mod.class_method_list.map(&:name)
+  end
+
+  def test_module_function_without_arguments_preserved_by_named_visibility
+    util_parser <<~RUBY
+      module M
+        def before; end
+        module_function
+        def first; end
+        public :first
+        private :before
+        def second; end
+        module_function :before
+        public def third; end
+        def fourth; end
+      end
+    RUBY
+    mod = @store.find_module_named 'M'
+    instance_methods = mod.method_list.reject(&:singleton)
+
+    assert_equal ['before', 'first', 'second', 'third', 'fourth'], instance_methods.map(&:name)
+    assert_equal [:private, :public, :private, :public, :private], instance_methods.map(&:visibility)
+    assert_equal ['first', 'second', 'before', 'third', 'fourth'], mod.class_method_list.map(&:name)
+    assert_equal [:public] * 5, mod.class_method_list.map(&:visibility)
+  end
+
+  def test_module_function_without_arguments_scoped
+    util_parser <<~RUBY
+      module M
+        module_function
+        module Nested
+          def ordinary; end
+          module_function
+          def nested; end
+        end
+        class C
+          def ordinary; end
+        end
+        class << self
+          private
+          def singleton; end
+        end
+        def outer; end
+      end
+      module M
+        def reopened; end
+      end
+      module Other
+        def ordinary; end
+      end
+    RUBY
+    mod = @store.find_module_named 'M'
+    nested = @store.find_module_named 'M::Nested'
+    klass = @store.find_class_named 'M::C'
+    other = @store.find_module_named 'Other'
+
+    assert_equal ['singleton', 'outer'], mod.class_method_list.map(&:name)
+    assert_equal [:private, :public], mod.class_method_list.map(&:visibility)
+    assert_equal :private, mod.find_method('outer', false).visibility
+    assert_equal :public, mod.find_method('reopened', false).visibility
+    assert_equal ['nested'], nested.class_method_list.map(&:name)
+    assert_equal :public, nested.find_method('ordinary', false).visibility
+    assert_equal :private, nested.find_method('nested', false).visibility
+    assert_equal [false], klass.method_list.map(&:singleton)
+    assert_equal [:public], klass.method_list.map(&:visibility)
+    assert_equal [false], other.method_list.map(&:singleton)
+    assert_equal [:public], other.method_list.map(&:visibility)
+  end
+
+  def test_module_function_without_arguments_explicit_receivers_and_attributes
+    util_parser <<~RUBY
+      class NilClass; end
+      module M
+        module_function
+        def self.explicit; end
+        def M.named; end
+        def nil.literal; end
+        attr_reader :reader
+        def implicit; end
+      end
+    RUBY
+    mod = @store.find_module_named 'M'
+    nil_class = @store.find_class_named 'NilClass'
+
+    assert_equal ['explicit', 'named', 'implicit'], mod.class_method_list.map(&:name)
+    assert_equal [:public] * 3, mod.class_method_list.map(&:visibility)
+    assert_equal ['implicit'], mod.method_list.reject(&:singleton).map(&:name)
+    assert_equal ['reader'], mod.attributes.map(&:name)
+    assert_equal [false], mod.attributes.map(&:singleton)
+    assert_equal [:private], mod.attributes.map(&:visibility)
+    assert_equal [false], nil_class.method_list.map(&:singleton)
+    assert_equal [:public], nil_class.method_list.map(&:visibility)
+  end
+
+  def test_module_function_without_arguments_initialize_and_documentation_directives
+    util_parser <<~RUBY
+      module M
+        module_function
+        def initialize(value); end
+        def omitted; end # :nodoc:
+        # :stopdoc:
+        def hidden; end
+        # :startdoc:
+        def resumed; end
+        # :enddoc:
+        def ended; end
+      end
+    RUBY
+    mod = @store.find_module_named 'M'
+
+    assert_equal ['initialize', 'initialize', 'resumed', 'resumed'], mod.method_list.map(&:name)
+    assert_equal [false, true, false, true], mod.method_list.map(&:singleton)
+    assert_equal [:private, :public, :private, :public], mod.method_list.map(&:visibility)
+  end
+
   def test_class_method_visibility
     util_parser <<~RUBY
       class A
@@ -2729,6 +2899,7 @@ def foo; end
           tap do end
           def foo; end
           module_function :foo
+          module_function
           def foo; end
         end
         def bar; end