diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -568,7 +568,6 @@
   __ranges/views.h
   __ranges/zip_view.h
   __split_buffer
-  __std_stream
   __string/char_traits.h
   __string/constexpr_c_functions.h
   __string/extern_template_lists.h
diff --git a/libcxx/include/libcxx.imp b/libcxx/include/libcxx.imp
--- a/libcxx/include/libcxx.imp
+++ b/libcxx/include/libcxx.imp
@@ -8,7 +8,6 @@
   { include: [ "<__node_handle>", "private", "<unordered_set>", "public" ] },
   { include: [ "<__split_buffer>", "private", "<deque>", "public" ] },
   { include: [ "<__split_buffer>", "private", "<vector>", "public" ] },
-  { include: [ "<__std_stream>", "private", "<iostream>", "public" ] },
   { include: [ "<__threading_support>", "private", "<atomic>", "public" ] },
   { include: [ "<__threading_support>", "private", "<mutex>", "public" ] },
   { include: [ "<__threading_support>", "private", "<semaphore>", "public" ] },
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -1725,10 +1725,6 @@
   module __mbstate_t         { private header "__mbstate_t.h"       export * }
   module __node_handle       { private header "__node_handle"       export * }
   module __split_buffer      { private header "__split_buffer"      export * }
-  module __std_stream        {
-    @requires_LIBCXX_ENABLE_LOCALIZATION@
-    private header "__std_stream" export *
-  }
   module __threading_support {         header "__threading_support" export * }
   module __tree              {         header "__tree"              export * }
   module __undef_macros      {         header "__undef_macros"      export * }
diff --git a/libcxx/include/__std_stream b/libcxx/src/__std_stream
rename from libcxx/include/__std_stream
rename to libcxx/src/__std_stream
diff --git a/libcxx/src/iostream.cpp b/libcxx/src/iostream.cpp
--- a/libcxx/src/iostream.cpp
+++ b/libcxx/src/iostream.cpp
@@ -7,7 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include <__locale>
-#include <__std_stream>
+#include "__std_stream"
 #include <new>
 #include <string>
 
diff --git a/libcxx/test/libcxx/private_headers.verify.cpp b/libcxx/test/libcxx/private_headers.verify.cpp
--- a/libcxx/test/libcxx/private_headers.verify.cpp
+++ b/libcxx/test/libcxx/private_headers.verify.cpp
@@ -599,7 +599,6 @@
 #include <__ranges/views.h> // expected-error@*:* {{use of private header from outside its module: '__ranges/views.h'}}
 #include <__ranges/zip_view.h> // expected-error@*:* {{use of private header from outside its module: '__ranges/zip_view.h'}}
 #include <__split_buffer> // expected-error@*:* {{use of private header from outside its module: '__split_buffer'}}
-#include <__std_stream> // expected-error@*:* {{use of private header from outside its module: '__std_stream'}}
 #include <__string/char_traits.h> // expected-error@*:* {{use of private header from outside its module: '__string/char_traits.h'}}
 #include <__string/constexpr_c_functions.h> // expected-error@*:* {{use of private header from outside its module: '__string/constexpr_c_functions.h'}}
 #include <__string/extern_template_lists.h> // expected-error@*:* {{use of private header from outside its module: '__string/extern_template_lists.h'}}
diff --git a/libcxx/utils/data/ignore_format.txt b/libcxx/utils/data/ignore_format.txt
--- a/libcxx/utils/data/ignore_format.txt
+++ b/libcxx/utils/data/ignore_format.txt
@@ -592,7 +592,6 @@
 libcxx/include/stdint.h
 libcxx/include/stdio.h
 libcxx/include/stdlib.h
-libcxx/include/__std_stream
 libcxx/include/streambuf
 libcxx/include/string
 libcxx/include/__string/char_traits.h
@@ -806,6 +805,7 @@
 libcxx/src/regex.cpp
 libcxx/src/shared_mutex.cpp
 libcxx/src/stdexcept.cpp
+libcxx/src/__std_stream
 libcxx/src/string.cpp
 libcxx/src/strstream.cpp
 libcxx/src/support/ibm/mbsnrtowcs.cpp
diff --git a/libcxx/utils/generate_iwyu_mapping.py b/libcxx/utils/generate_iwyu_mapping.py
--- a/libcxx/utils/generate_iwyu_mapping.py
+++ b/libcxx/utils/generate_iwyu_mapping.py
@@ -53,7 +53,6 @@
         elif i == '__mutex_base': continue
         elif i == '__node_handle': public = ['map', 'set', 'unordered_map', 'unordered_set']
         elif i == '__split_buffer': public = ['deque', 'vector']
-        elif i == '__std_stream': public = ['iostream']
         elif i == '__threading_support': public = ['atomic', 'mutex', 'semaphore', 'thread']
         elif i == '__tree': public = ['map', 'set']
         elif i == '__undef_macros': continue