diff --git a/Directory.Build.props b/Directory.Build.props
index 5cb87bb7c25725..54ae373485c0fa 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -210,6 +210,10 @@
     <MicrosoftNetCoreAppRuntimePackNativeDir>$([MSBuild]::NormalizeDirectory('$(MicrosoftNetCoreAppRuntimePackRidDir)', 'native'))</MicrosoftNetCoreAppRuntimePackNativeDir>
   </PropertyGroup>
 
+  <PropertyGroup>
+    <DotNetHostBinDir>$([MSBuild]::NormalizeDirectory('$(ArtifactsBinDir)', '$(OutputRid).$(Configuration)', 'corehost'))</DotNetHostBinDir>
+  </PropertyGroup>
+
   <!--Feature switches -->
   <PropertyGroup>
     <EnableNgenOptimization Condition="'$(EnableNgenOptimization)' == '' and ('$(Configuration)' == 'Release' or '$(Configuration)' == 'Checked')">true</EnableNgenOptimization>
diff --git a/eng/Subsets.props b/eng/Subsets.props
index b2292ac98e61c8..be4c6a8862480b 100644
--- a/eng/Subsets.props
+++ b/eng/Subsets.props
@@ -120,7 +120,14 @@
     <SubsetName Include="Mono.WasmRuntime" Description="The WebAssembly runtime." />
     <SubsetName Include="Mono.MsCorDbi" Description="The implementation of ICorDebug interface." />
     <SubsetName Include="Mono.Workloads" OnDemand="true" Description="Builds the installers and the insertion metadata for Blazor workloads." />
-    
+
+    <!-- Host -->
+    <SubsetName Include="Host" Description="The .NET hosts, packages, hosting libraries, and tests." />
+    <SubsetName Include="Host.Native" Description="The .NET hosts." />
+    <SubsetName Include="Host.Pkg" Description="The .NET host packages." />
+    <SubsetName Include="Host.Tools" Description="The .NET hosting libraries." />
+    <SubsetName Include="Host.Tests" Description="The .NET hosting tests." />
+
     <!-- Libs -->
     <SubsetName Include="Libs" Description="The libraries native part, refs and source assemblies, test infra and packages, but NOT the tests (use Libs.Tests to request those explicitly)" />
     <SubsetName Include="Libs.Native" Description="The native libraries used in the shared framework." />
@@ -130,13 +137,6 @@
     <SubsetName Include="Libs.Packages" Description="The projects that produce NuGet packages from libraries." />
     <SubsetName Include="Libs.Tests" OnDemand="true" Description="The test projects. Note that building this doesn't execute tests: you must also pass the '-test' argument." />
 
-    <!-- Host -->
-    <SubsetName Include="Host" Description="The .NET hosts, packages, hosting libraries, and tests." />
-    <SubsetName Include="Host.Native" Description="The .NET hosts." />
-    <SubsetName Include="Host.Pkg" Description="The .NET host packages." />
-    <SubsetName Include="Host.Tools" Description="The .NET hosting libraries." />
-    <SubsetName Include="Host.Tests" Description="The .NET hosting tests." />
-
     <!-- Packs -->
     <SubsetName Include="Packs" Description="Builds the shared framework packs, archives, bundles, installers, and the framework pack tests." />
     <SubsetName Include="Packs.Product" Description="Builds the shared framework packs, archives, bundles, and installers." />
@@ -263,6 +263,22 @@
     <ProjectToBuild Include="$(WorkloadsProjectRoot)\workloads.csproj" Category="mono" />
   </ItemGroup>
 
+  <!-- Host sets -->
+  <ItemGroup Condition="$(_subset.Contains('+host.native+'))">
+    <CorehostProjectToBuild Include="$(SharedNativeRoot)corehost\corehost.proj" SignPhase="Binaries" BuildInParallel="false" />
+    <ProjectToBuild Include="@(CorehostProjectToBuild)" Pack="true" Category="host" />
+  </ItemGroup>
+
+  <ItemGroup Condition="$(_subset.Contains('+host.tools+'))">
+    <ManagedProjectToBuild Include="$(InstallerProjectRoot)managed\**\*.csproj" SignPhase="Binaries" />
+    <ProjectToBuild Include="@(ManagedProjectToBuild)" BuildInParallel="true" Pack="true" Category="host" />
+  </ItemGroup>
+
+  <ItemGroup Condition="$(_subset.Contains('+host.pkg+')) and '$(PgoInstrument)' != 'true'">
+    <PkgprojProjectToBuild Include="$(InstallerProjectRoot)pkg\projects\host-packages.proj" SignPhase="MsiFiles" BuildInParallel="false" />
+    <ProjectToBuild Include="@(PkgprojProjectToBuild)" Pack="true" Category="host" />
+  </ItemGroup>
+
   <!-- Libraries sets -->
   <ItemGroup Condition="$(_subset.Contains('+libs.native+'))">
     <ProjectToBuild Include="$(LibrariesProjectRoot)Native\build-native.proj" Category="libs" />
@@ -288,22 +304,7 @@
     <ProjectToBuild Include="$(LibrariesProjectRoot)tests.proj" Category="libs" Test="true" />
   </ItemGroup>
 
-  <!-- Host sets -->
-  <ItemGroup Condition="$(_subset.Contains('+host.native+'))">
-    <CorehostProjectToBuild Include="$(SharedNativeRoot)corehost\corehost.proj" SignPhase="Binaries" BuildInParallel="false" />
-    <ProjectToBuild Include="@(CorehostProjectToBuild)" Pack="true" Category="host" />
-  </ItemGroup>
-
-  <ItemGroup Condition="$(_subset.Contains('+host.tools+'))">
-    <ManagedProjectToBuild Include="$(InstallerProjectRoot)managed\**\*.csproj" SignPhase="Binaries" />
-    <ProjectToBuild Include="@(ManagedProjectToBuild)" BuildInParallel="true" Pack="true" Category="host" />
-  </ItemGroup>
-
-  <ItemGroup Condition="$(_subset.Contains('+host.pkg+')) and '$(PgoInstrument)' != 'true'">
-    <PkgprojProjectToBuild Include="$(InstallerProjectRoot)pkg\projects\host-packages.proj" SignPhase="MsiFiles" BuildInParallel="false" />
-    <ProjectToBuild Include="@(PkgprojProjectToBuild)" Pack="true" Category="host" />
-  </ItemGroup>
-
+  <!-- Host.tests subset (consumes live built libraries assets so needs to come after libraries) -->
   <ItemGroup Condition="$(_subset.Contains('+host.tests+'))">
     <TestProjectToBuild Include="$(InstallerProjectRoot)tests\Microsoft.NET.HostModel.Tests\AppHost.Bundle.Tests\AppHost.Bundle.Tests.csproj" />
     <TestProjectToBuild Include="$(InstallerProjectRoot)tests\Microsoft.NET.HostModel.Tests\Microsoft.NET.HostModel.AppHost.Tests\Microsoft.NET.HostModel.AppHost.Tests.csproj" />
diff --git a/eng/pipelines/common/platform-matrix.yml b/eng/pipelines/common/platform-matrix.yml
index 15fe948e92967e..244240a68f32fb 100644
--- a/eng/pipelines/common/platform-matrix.yml
+++ b/eng/pipelines/common/platform-matrix.yml
@@ -205,6 +205,32 @@ jobs:
         ${{ insert }}: ${{ parameters.jobParameters }}
         buildingOnSourceBuildImage: true
 
+# Linux s390x
+
+- ${{ if containsValue(parameters.platforms, 'Linux_s390x') }}:
+  - template: xplat-setup.yml
+    parameters:
+      jobTemplate: ${{ parameters.jobTemplate }}
+      helixQueuesTemplate: ${{ parameters.helixQueuesTemplate }}
+      variables: ${{ parameters.variables }}
+      osGroup: Linux
+      archType: s390x
+      targetRid: linux-s390x
+      platform: Linux_s390x
+      container:
+        image: ubuntu-18.04-cross-s390x-20201102145728-d6e0352
+        registry: mcr
+      jobParameters:
+        runtimeFlavor: ${{ parameters.runtimeFlavor }}
+        stagedBuild: ${{ parameters.stagedBuild }}
+        buildConfig: ${{ parameters.buildConfig }}
+        ${{ if eq(parameters.passPlatforms, true) }}:
+          platforms: ${{ parameters.platforms }}
+        helixQueueGroup: ${{ parameters.helixQueueGroup }}
+        crossBuild: true
+        crossrootfsDir: '/crossrootfs/s390x'
+        ${{ insert }}: ${{ parameters.jobParameters }}
+
 # WebAssembly
 
 - ${{ if containsValue(parameters.platforms, 'Browser_wasm') }}:
diff --git a/eng/pipelines/common/variables.yml b/eng/pipelines/common/variables.yml
index c724f4beb367f9..e2ed01f836cf55 100644
--- a/eng/pipelines/common/variables.yml
+++ b/eng/pipelines/common/variables.yml
@@ -14,9 +14,10 @@ variables:
 - name: isFullMatrix
   value: ${{ and(eq(variables['System.TeamProject'], 'public'), ne(variables['Build.Reason'], 'PullRequest')) }}
 
-# We only run evaluate paths on runtime and runtime-staging pipelines on PRs
+# We only run evaluate paths on runtime, runtime-staging and runtime-community pipelines on PRs
+# keep in sync with /eng/pipelines/common/xplat-setup.yml
 - name: dependOnEvaluatePaths
-  value: ${{ and(eq(variables['Build.Reason'], 'PullRequest'), in(variables['Build.DefinitionName'], 'runtime', 'runtime-staging')) }}
+  value: ${{ and(eq(variables['Build.Reason'], 'PullRequest'), in(variables['Build.DefinitionName'], 'runtime', 'runtime-staging', 'runtime-community')) }}
 - name: debugOnPrReleaseOnRolling
   ${{ if ne(variables['Build.Reason'], 'PullRequest') }}:
     value: Release
diff --git a/eng/pipelines/common/xplat-setup.yml b/eng/pipelines/common/xplat-setup.yml
index 2010c653f89cc2..9c9861e3a963f1 100644
--- a/eng/pipelines/common/xplat-setup.yml
+++ b/eng/pipelines/common/xplat-setup.yml
@@ -22,7 +22,7 @@ jobs:
     shouldContinueOnError: ${{ and(endsWith(variables['Build.DefinitionName'], 'staging'), eq(variables['Build.Reason'], 'PullRequest')) }}
 
     # keep in sync with /eng/pipelines/common/variables.yml
-    dependOnEvaluatePaths: ${{ and(eq(variables['Build.Reason'], 'PullRequest'), in(variables['Build.DefinitionName'], 'runtime', 'runtime-staging')) }}
+    dependOnEvaluatePaths: ${{ and(eq(variables['Build.Reason'], 'PullRequest'), in(variables['Build.DefinitionName'], 'runtime', 'runtime-staging', 'runtime-community')) }}
 
     variables:
       # Disable component governance in our CI builds. These builds are not shipping nor
diff --git a/eng/pipelines/libraries/helix-queues-setup.yml b/eng/pipelines/libraries/helix-queues-setup.yml
index 880aa8939932c0..3dc5d4dc2ee604 100644
--- a/eng/pipelines/libraries/helix-queues-setup.yml
+++ b/eng/pipelines/libraries/helix-queues-setup.yml
@@ -85,6 +85,10 @@ jobs:
         # Limiting interp runs as we don't need as much coverage.
         - Debian.9.Amd64.Open
 
+    # Linux s390x
+    - ${{ if eq(parameters.platform, 'Linux_s390x') }}:
+        - Ubuntu.2004.S390X.Experimental.Open
+
     # OSX arm64
     - ${{ if eq(parameters.platform, 'OSX_arm64') }}:
       - OSX.1100.ARM64.Open
diff --git a/eng/pipelines/runtime-community.yml b/eng/pipelines/runtime-community.yml
new file mode 100644
index 00000000000000..9ecb1f2677ae2d
--- /dev/null
+++ b/eng/pipelines/runtime-community.yml
@@ -0,0 +1,60 @@
+trigger: none
+
+schedules:
+  - cron: "0 7,19 * * *" # run at 7:00 and 19:00 (UTC) which is 23:00 and 11:00 (PST).
+    displayName: Runtime-community default schedule
+    branches:
+      include:
+      - main
+      - release/*.*
+    always: false # run only if there were changes since the last successful scheduled run.
+
+variables:
+  - template: /eng/pipelines/common/variables.yml
+
+jobs:
+#
+# Evaluate paths
+#
+- ${{ if eq(variables.dependOnEvaluatePaths, true) }}:
+  - template: /eng/pipelines/common/evaluate-default-paths.yml
+
+#
+# s390x
+# Build the whole product using Mono and run libraries tests
+#
+- template: /eng/pipelines/common/platform-matrix.yml
+  parameters:
+    jobTemplate: /eng/pipelines/common/global-build-job.yml
+    helixQueuesTemplate: /eng/pipelines/libraries/helix-queues-setup.yml
+    buildConfig: Release
+    runtimeFlavor: mono
+    platforms:
+    - Linux_s390x
+    variables:
+      # map dependencies variables to local variables
+      - name: librariesContainsChange
+        value: $[ dependencies.evaluate_paths.outputs['SetPathVars_libraries.containsChange'] ]
+      - name: monoContainsChange
+        value: $[ dependencies.evaluate_paths.outputs['SetPathVars_mono.containsChange'] ]
+    jobParameters:
+      testGroup: innerloop
+      nameSuffix: AllSubsets_Mono
+      buildArgs: -s mono+libs+host+packs+libs.tests -c $(_BuildConfig) /p:ArchiveTests=true
+      timeoutInMinutes: 180
+      condition: >-
+        or(
+          eq(dependencies.evaluate_paths.outputs['SetPathVars_libraries.containsChange'], true),
+          eq(dependencies.evaluate_paths.outputs['SetPathVars_mono.containsChange'], true),
+          eq(dependencies.evaluate_paths.outputs['SetPathVars_installer.containsChange'], true),
+          eq(variables['isFullMatrix'], true))
+      # extra steps, run tests
+      extraStepsTemplate: /eng/pipelines/libraries/helix.yml
+      extraStepsParameters:
+        creator: dotnet-bot
+        testRunNamePrefixSuffix: Mono_$(_BuildConfig)
+        condition: >-
+          or(
+          eq(variables['librariesContainsChange'], true),
+          eq(variables['monoContainsChange'], true),
+          eq(variables['isFullMatrix'], true))
diff --git a/src/installer/pkg/Directory.Build.props b/src/installer/pkg/Directory.Build.props
index 10f36b399c73b6..f51718676368a2 100644
--- a/src/installer/pkg/Directory.Build.props
+++ b/src/installer/pkg/Directory.Build.props
@@ -3,7 +3,6 @@
 
   <PropertyGroup>
     <Platform>$(TargetArchitecture)</Platform>
-    <DotNetHostBinDir>$(ArtifactsBinDir)$(OutputRid).$(Configuration)\corehost</DotNetHostBinDir>
   </PropertyGroup>
 
   <PropertyGroup>
diff --git a/src/libraries/externals.csproj b/src/libraries/externals.csproj
index 6ef3ddc0f19015..969ed9603a2cda 100644
--- a/src/libraries/externals.csproj
+++ b/src/libraries/externals.csproj
@@ -9,6 +9,7 @@
     <BinPlaceNative>true</BinPlaceNative>
     <BinPlaceRuntime>false</BinPlaceRuntime>
     <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>
+    <UseLiveBuiltDotNetHost Condition="'$(TargetArchitecture)' == 's390x'">true</UseLiveBuiltDotNetHost>
   </PropertyGroup>
 
   <ItemGroup Condition="'$(DotNetBuildFromSource)' != 'true'">
@@ -16,7 +17,7 @@
                       Version="$(MicrosoftDiaSymReaderNativeVersion)" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetsMobile)' != 'true'">
+  <ItemGroup Condition="'$(TargetsMobile)' != 'true' and '$(UseLiveBuiltDotNetHost)' != 'true'">
     <PackageReference Include="Microsoft.NETCore.DotNetHost"
                       Version="$(MicrosoftNETCoreDotNetHostVersion)" />
     <PackageReference Include="Microsoft.NETCore.DotNetHostPolicy"
@@ -38,17 +39,31 @@
       <ReferenceCopyLocalPaths Remove="@(ReferenceCopyLocalPaths)" Condition="'%(Filename)' == 'apphost'" />
     </ItemGroup>
 
-    <ItemGroup>
+    <ItemGroup Condition="'$(UseLiveBuiltDotNetHost)' != 'true'">
       <HostFxFile Include="@(ReferenceCopyLocalPaths)" Condition="'%(ReferenceCopyLocalPaths.Filename)' == 'hostfxr' or
                                                                   '%(ReferenceCopyLocalPaths.Filename)' == 'libhostfxr'" />
       <DotnetExe Include="@(ReferenceCopyLocalPaths)" Condition="'%(ReferenceCopyLocalPaths.Filename)' == 'dotnet'" />
     </ItemGroup>
 
+    <ItemGroup Condition="'$(UseLiveBuiltDotNetHost)' == 'true'">
+      <CoreHostFiles Include="$(DotNetHostBinDir)*" />
+      <HostFxFile Include="@(CoreHostFiles)" Condition="'%(CoreHostFiles.Filename)' == 'hostfxr' or
+                                                          '%(CoreHostFiles.Filename)' == 'libhostfxr'" />
+      <HostPolicyFile Include="@(CoreHostFiles)" Condition="'%(CoreHostFiles.Filename)' == 'hostpolicy' or
+                                                              '%(CoreHostFiles.Filename)' == 'libhostpolicy'" />
+      <DotnetExe Include="@(CoreHostFiles)" Condition="'%(CoreHostFiles.Filename)' == 'dotnet'" />
+    </ItemGroup>
+
     <Copy SourceFiles="@(HostFxFile)"
           DestinationFolder="$(NetCoreAppCurrentTestHostPath)host\fxr\$(ProductVersion)"
           SkipUnchangedFiles="true"
           UseHardlinksIfPossible="$(UseHardlink)" />
 
+    <Copy SourceFiles="@(HostPolicyFile)"
+          DestinationFolder="$(NetCoreAppCurrentTestHostPath)shared\Microsoft.NETCore.App\$(ProductVersion)"
+          SkipUnchangedFiles="true"
+          UseHardlinksIfPossible="$(UseHardlink)" />
+
     <Copy SourceFiles="@(DotnetExe)"
           DestinationFolder="$(NetCoreAppCurrentTestHostPath)"
           SkipUnchangedFiles="true"
diff --git a/src/libraries/tests.proj b/src/libraries/tests.proj
index 8c0fc9060c28ac..c85b97c3c94b3d 100644
--- a/src/libraries/tests.proj
+++ b/src/libraries/tests.proj
@@ -258,6 +258,10 @@
     <ProjectExclusions Include="$(MSBuildThisFileDirectory)System.Security.Cryptography.OpenSsl/tests/System.Security.Cryptography.OpenSsl.Tests.csproj" />
   </ItemGroup>
 
+  <ItemGroup Condition="'$(TargetArchitecture)' == 's390x' and '$(RunDisableds390xTests)' != 'true'">
+    <ProjectExclusions Include="$(MSBuildThisFileDirectory)System.Drawing.Common\tests\System.Drawing.Common.Tests.csproj" />
+  </ItemGroup>
+
   <ItemGroup Condition="'$(TestSingleFile)' == 'true'">
     <!-- Run only a small randomly chosen set of passing test suites -->
     <ProjectExclusions Include="$(MSBuildThisFileDirectory)*\tests\**\*.Tests.csproj" />
diff --git a/src/mono/mono.proj b/src/mono/mono.proj
index dd8140fb81e8be..fb98ffc1896906 100644
--- a/src/mono/mono.proj
+++ b/src/mono/mono.proj
@@ -506,6 +506,7 @@
       <_Objcopy>objcopy</_Objcopy>
       <_Objcopy Condition="'$(Platform)' == 'arm'">arm-linux-$(_LinuxAbi)eabi$(_LinuxFloatAbi)-$(_Objcopy)</_Objcopy>
       <_Objcopy Condition="'$(Platform)' == 'arm64'">aarch64-linux-$(_LinuxAbi)-$(_Objcopy)</_Objcopy>
+      <_Objcopy Condition="'$(Platform)' == 's390x'">s390x-linux-$(_LinuxAbi)-$(_Objcopy)</_Objcopy>
       <_Objcopy Condition="'$(Platform)' == 'x64'">x86_64-linux-$(_LinuxAbi)-$(_Objcopy)</_Objcopy>
       <_Objcopy Condition="'$(Platform)' == 'x86'">i686-linux-$(_LinuxAbi)-$(_Objcopy)</_Objcopy>
       <_Objcopy Condition="'$(TargetsAndroid)' == 'true'">$(ANDROID_NDK_ROOT)/toolchains/llvm/prebuilt/$(MonoToolchainPrebuiltOS)/bin/$(_Objcopy)</_Objcopy>