diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -218,6 +218,7 @@
   __functional/weak_result_type.h
   __functional_base
   __hash_table
+  __ios/fpos.h
   __iterator/access.h
   __iterator/advance.h
   __iterator/back_insert_iterator.h
diff --git a/libcxx/include/__ios/fpos.h b/libcxx/include/__ios/fpos.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__ios/fpos.h
@@ -0,0 +1,79 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___IOS_FPOS_H
+#define _LIBCPP___IOS_FPOS_H
+
+#include <__config>
+#include <iosfwd>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _StateT>
+class _LIBCPP_TEMPLATE_VIS fpos {
+private:
+  _StateT __st_;
+  streamoff __off_;
+
+public:
+  _LIBCPP_HIDE_FROM_ABI fpos(streamoff __off = streamoff()) : __st_(), __off_(__off) {}
+
+  _LIBCPP_HIDE_FROM_ABI operator streamoff() const { return __off_; }
+
+  _LIBCPP_HIDE_FROM_ABI _StateT state() const { return __st_; }
+  _LIBCPP_HIDE_FROM_ABI void state(_StateT __st) { __st_ = __st; }
+
+  _LIBCPP_HIDE_FROM_ABI fpos& operator+=(streamoff __off) {
+    __off_ += __off;
+    return *this;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI fpos operator+(streamoff __off) const {
+    fpos __t(*this);
+    __t += __off;
+    return __t;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI fpos& operator-=(streamoff __off) {
+    __off_ -= __off;
+    return *this;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI fpos operator-(streamoff __off) const {
+    fpos __t(*this);
+    __t -= __off;
+    return __t;
+  }
+};
+
+template <class _StateT>
+inline _LIBCPP_HIDE_FROM_ABI
+streamoff operator-(const fpos<_StateT>& __x, const fpos<_StateT>& __y) {
+  return streamoff(__x) - streamoff(__y);
+}
+
+template <class _StateT>
+inline _LIBCPP_HIDE_FROM_ABI
+bool operator==(const fpos<_StateT>& __x, const fpos<_StateT>& __y) {
+  return streamoff(__x) == streamoff(__y);
+}
+
+template <class _StateT>
+inline _LIBCPP_HIDE_FROM_ABI
+bool operator!=(const fpos<_StateT>& __x, const fpos<_StateT>& __y) {
+  return streamoff(__x) != streamoff(__y);
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___IOS_FPOS_H
diff --git a/libcxx/include/ios b/libcxx/include/ios
--- a/libcxx/include/ios
+++ b/libcxx/include/ios
@@ -211,6 +211,7 @@
 */
 
 #include <__config>
+#include <__ios/fpos.h>
 #include <__locale>
 #include <iosfwd>
 #include <system_error>
diff --git a/libcxx/include/module.modulemap b/libcxx/include/module.modulemap
--- a/libcxx/include/module.modulemap
+++ b/libcxx/include/module.modulemap
@@ -575,6 +575,10 @@
     header "ios"
     export iosfwd
     export *
+
+    module __ios {
+      module fpos { private header "__ios/fpos.h" }
+    }
   }
   module iosfwd {
     header "iosfwd"
diff --git a/libcxx/include/string b/libcxx/include/string
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -521,6 +521,7 @@
 #include <__config>
 #include <__debug>
 #include <__functional_base>
+#include <__ios/fpos.h>
 #include <__iterator/wrap_iter.h>
 #include <algorithm>
 #include <compare>
@@ -538,11 +539,11 @@
 #include <version>
 
 #ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
-#   include <cwchar>
+#  include <cwchar>
 #endif
 
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
-# include <cstdint>
+#  include <cstdint>
 #endif
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -555,43 +556,6 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-// fpos
-
-template <class _StateT>
-class _LIBCPP_TEMPLATE_VIS fpos
-{
-private:
-    _StateT __st_;
-    streamoff __off_;
-public:
-    _LIBCPP_INLINE_VISIBILITY fpos(streamoff __off = streamoff()) : __st_(), __off_(__off) {}
-
-    _LIBCPP_INLINE_VISIBILITY operator streamoff() const {return __off_;}
-
-    _LIBCPP_INLINE_VISIBILITY _StateT state() const {return __st_;}
-    _LIBCPP_INLINE_VISIBILITY void state(_StateT __st) {__st_ = __st;}
-
-    _LIBCPP_INLINE_VISIBILITY fpos& operator+=(streamoff __off) {__off_ += __off; return *this;}
-    _LIBCPP_INLINE_VISIBILITY fpos  operator+ (streamoff __off) const {fpos __t(*this); __t += __off; return __t;}
-    _LIBCPP_INLINE_VISIBILITY fpos& operator-=(streamoff __off) {__off_ -= __off; return *this;}
-    _LIBCPP_INLINE_VISIBILITY fpos  operator- (streamoff __off) const {fpos __t(*this); __t -= __off; return __t;}
-};
-
-template <class _StateT>
-inline _LIBCPP_INLINE_VISIBILITY
-streamoff operator-(const fpos<_StateT>& __x, const fpos<_StateT>& __y)
-    {return streamoff(__x) - streamoff(__y);}
-
-template <class _StateT>
-inline _LIBCPP_INLINE_VISIBILITY
-bool operator==(const fpos<_StateT>& __x, const fpos<_StateT>& __y)
-    {return streamoff(__x) == streamoff(__y);}
-
-template <class _StateT>
-inline _LIBCPP_INLINE_VISIBILITY
-bool operator!=(const fpos<_StateT>& __x, const fpos<_StateT>& __y)
-    {return streamoff(__x) != streamoff(__y);}
-
 // basic_string
 
 template<class _CharT, class _Traits, class _Allocator>
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/ios/fpos.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/ios/fpos.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/ios/fpos.module.verify.cpp
@@ -0,0 +1,15 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__ios/fpos.h'}}
+#include <__ios/fpos.h>
diff --git a/libcxx/test/std/input.output/iostreams.base/fpos/fpos.operations/fpos.pass.cpp b/libcxx/test/std/input.output/iostreams.base/fpos/fpos.operations/fpos.pass.cpp
--- a/libcxx/test/std/input.output/iostreams.base/fpos/fpos.operations/fpos.pass.cpp
+++ b/libcxx/test/std/input.output/iostreams.base/fpos/fpos.operations/fpos.pass.cpp
@@ -6,16 +6,16 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "test_macros.h"
+// <ios>
+
+// template <class stateT>
+// class fpos;
 
-#include <string>
 #include <cassert>
+#include <ios>
 #include <type_traits>
 
-// <string>
-
-// template <class stateT>
-// class fpos;
+#include "test_macros.h"
 
 template<class T, class = void>
 struct is_equality_comparable : std::false_type { };