diff --git a/Misc/NEWS.d/next/Build/2019-02-02-13-34-05.bpo-34691.B-Lsj4.rst b/Misc/NEWS.d/next/Build/2019-02-02-13-34-05.bpo-34691.B-Lsj4.rst
new file mode 100644
index 00000000000000..3b5aca75103b75
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2019-02-02-13-34-05.bpo-34691.B-Lsj4.rst
@@ -0,0 +1,2 @@
+The _contextvars module is now built into the core Python library on
+Windows.
diff --git a/PC/config.c b/PC/config.c
index 43347dddeba322..6f34962bd72d4f 100644
--- a/PC/config.c
+++ b/PC/config.c
@@ -72,6 +72,8 @@ extern PyObject* PyInit__string(void);
 extern PyObject* PyInit__stat(void);
 extern PyObject* PyInit__opcode(void);
 
+extern PyObject* PyInit__contextvars(void);
+
 /* tools/freeze/makeconfig.py marker for additional "extern" */
 /* -- ADDMODULE MARKER 1 -- */
 
@@ -164,6 +166,8 @@ struct _inittab _PyImport_Inittab[] = {
     {"_stat", PyInit__stat},
     {"_opcode", PyInit__opcode},
 
+    {"_contextvars", PyInit__contextvars},
+
     /* Sentinel */
     {0, 0}
 };
diff --git a/PCbuild/_contextvars.vcxproj b/PCbuild/_contextvars.vcxproj
deleted file mode 100644
index 7418e86570acb0..00000000000000
--- a/PCbuild/_contextvars.vcxproj
+++ /dev/null
@@ -1,77 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
-  <ItemGroup Label="ProjectConfigurations">
-    <ProjectConfiguration Include="Debug|Win32">
-      <Configuration>Debug</Configuration>
-      <Platform>Win32</Platform>
-    </ProjectConfiguration>
-    <ProjectConfiguration Include="Debug|x64">
-      <Configuration>Debug</Configuration>
-      <Platform>x64</Platform>
-    </ProjectConfiguration>
-    <ProjectConfiguration Include="PGInstrument|Win32">
-      <Configuration>PGInstrument</Configuration>
-      <Platform>Win32</Platform>
-    </ProjectConfiguration>
-    <ProjectConfiguration Include="PGInstrument|x64">
-      <Configuration>PGInstrument</Configuration>
-      <Platform>x64</Platform>
-    </ProjectConfiguration>
-    <ProjectConfiguration Include="PGUpdate|Win32">
-      <Configuration>PGUpdate</Configuration>
-      <Platform>Win32</Platform>
-    </ProjectConfiguration>
-    <ProjectConfiguration Include="PGUpdate|x64">
-      <Configuration>PGUpdate</Configuration>
-      <Platform>x64</Platform>
-    </ProjectConfiguration>
-    <ProjectConfiguration Include="Release|Win32">
-      <Configuration>Release</Configuration>
-      <Platform>Win32</Platform>
-    </ProjectConfiguration>
-    <ProjectConfiguration Include="Release|x64">
-      <Configuration>Release</Configuration>
-      <Platform>x64</Platform>
-    </ProjectConfiguration>
-  </ItemGroup>
-  <PropertyGroup Label="Globals">
-    <ProjectGuid>{B8BF1D81-09DC-42D4-B406-4F868B33A89E}</ProjectGuid>
-    <RootNamespace>_contextvars</RootNamespace>
-    <Keyword>Win32Proj</Keyword>
-  </PropertyGroup>
-  <Import Project="python.props" />
-  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Default.props" />
-  <PropertyGroup Label="Configuration">
-    <ConfigurationType>DynamicLibrary</ConfigurationType>
-    <CharacterSet>NotSet</CharacterSet>
-  </PropertyGroup>
-  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
-  <PropertyGroup>
-    <TargetExt>.pyd</TargetExt>
-  </PropertyGroup>
-  <ImportGroup Label="ExtensionSettings">
-  </ImportGroup>
-  <ImportGroup Label="PropertySheets">
-    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
-    <Import Project="pyproject.props" />
-  </ImportGroup>
-  <PropertyGroup Label="UserMacros" />
-  <PropertyGroup>
-    <_ProjectFileVersion>10.0.30319.1</_ProjectFileVersion>
-  </PropertyGroup>
-  <ItemGroup>
-    <ClCompile Include="..\Modules\_contextvarsmodule.c" />
-  </ItemGroup>
-  <ItemGroup>
-    <ResourceCompile Include="..\PC\python_nt.rc" />
-  </ItemGroup>
-  <ItemGroup>
-    <ProjectReference Include="pythoncore.vcxproj">
-      <Project>{cf7ac3d1-e2df-41d2-bea6-1e2556cdea26}</Project>
-      <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
-    </ProjectReference>
-  </ItemGroup>
-  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
-  <ImportGroup Label="ExtensionTargets">
-  </ImportGroup>
-</Project>
diff --git a/PCbuild/_contextvars.vcxproj.filters b/PCbuild/_contextvars.vcxproj.filters
deleted file mode 100644
index b3002b7ff6772e..00000000000000
--- a/PCbuild/_contextvars.vcxproj.filters
+++ /dev/null
@@ -1,16 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
-  <ItemGroup>
-    <ResourceCompile Include="..\PC\python_nt.rc" />
-  </ItemGroup>
-  <ItemGroup>
-    <Filter Include="Source Files">
-      <UniqueIdentifier>{7CBD8910-233D-4E9A-9164-9BA66C1F0E6D}</UniqueIdentifier>
-    </Filter>
-  </ItemGroup>
-  <ItemGroup>
-    <ClCompile Include="..\Modules\_contextvarsmodule.c">
-      <Filter>Source Files</Filter>
-    </ClCompile>
-  </ItemGroup>
-</Project>
diff --git a/PCbuild/pcbuild.proj b/PCbuild/pcbuild.proj
index befaa1fed76b00..dbe30dd6a8a898 100644
--- a/PCbuild/pcbuild.proj
+++ b/PCbuild/pcbuild.proj
@@ -50,7 +50,7 @@
     <!-- pyshellext.dll -->
     <Projects Include="pyshellext.vcxproj" />
     <!-- Extension modules -->
-    <ExtensionModules Include="_asyncio;_contextvars;_ctypes;_decimal;_elementtree;_msi;_multiprocessing;_overlapped;pyexpat;_queue;select;unicodedata;winsound" />
+    <ExtensionModules Include="_asyncio;_ctypes;_decimal;_elementtree;_msi;_multiprocessing;_overlapped;pyexpat;_queue;select;unicodedata;winsound" />
     <!-- Extension modules that require external sources -->
     <ExternalModules Include="_bz2;_lzma;_sqlite3" />
     <!-- venv launchers -->
diff --git a/Tools/msi/lib/lib_files.wxs b/Tools/msi/lib/lib_files.wxs
index 4bd0c57e3229db..a9952bdac4db91 100644
--- a/Tools/msi/lib/lib_files.wxs
+++ b/Tools/msi/lib/lib_files.wxs
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Wix xmlns="http://schemas.microsoft.com/wix/2006/wi">
-    <?define exts=pyexpat;select;unicodedata;winsound;_bz2;_elementtree;_socket;_ssl;_msi;_ctypes;_hashlib;_multiprocessing;_lzma;_decimal;_overlapped;_sqlite3;_asyncio;_queue;_contextvars ?>
+    <?define exts=pyexpat;select;unicodedata;winsound;_bz2;_elementtree;_socket;_ssl;_msi;_ctypes;_hashlib;_multiprocessing;_lzma;_decimal;_overlapped;_sqlite3;_asyncio;_queue ?>
     <Fragment>
         <DirectoryRef Id="Lib_venv_scripts_nt" />