diff --git a/.gitmodules b/.gitmodules
index ac507adcd40..94d4afb6c0f 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -5,7 +5,7 @@
 [submodule "external/mono"]
 	path = external/mono
 	url = https://github.com/mono/mono.git
-	branch = 2017-10
+	branch = 2017-12
 [submodule "external/mxe"]
 	path = external/mxe
 	url = https://github.com/xamarin/mxe.git
diff --git a/Configuration.props b/Configuration.props
index 64ff9cad573..9482200789b 100644
--- a/Configuration.props
+++ b/Configuration.props
@@ -54,8 +54,8 @@
     <JavaInteropSourceDirectory Condition=" '$(JavaInteropSourceDirectory)' == '' ">$(MSBuildThisFileDirectory)external\Java.Interop</JavaInteropSourceDirectory>
     <LlvmSourceDirectory Condition=" '$(LlvmSourceDirectory)' == '' ">$(MSBuildThisFileDirectory)external\llvm</LlvmSourceDirectory>
     <MonoSourceDirectory>$(MSBuildThisFileDirectory)external\mono</MonoSourceDirectory>
-    <MonoRequiredMinimumVersion Condition=" '$(MonoRequiredMinimumVersion)' == '' ">5.8.0</MonoRequiredMinimumVersion>
-    <MonoRequiredMaximumVersion Condition=" '$(MonoRequiredMaximumVersion)' == '' ">5.9.0</MonoRequiredMaximumVersion>
+    <MonoRequiredMinimumVersion Condition=" '$(MonoRequiredMinimumVersion)' == '' ">5.10.0</MonoRequiredMinimumVersion>
+    <MonoRequiredMaximumVersion Condition=" '$(MonoRequiredMaximumVersion)' == '' ">5.11.0</MonoRequiredMaximumVersion>
     <IgnoreMaxMonoVersion Condition=" '$(IgnoreMaxMonoVersion)' == '' ">True</IgnoreMaxMonoVersion>
     <MonoRequiredDarwinMinimumVersion>$(MonoRequiredMinimumVersion).22</MonoRequiredDarwinMinimumVersion>
     <LinkerSourceDirectory>$(MSBuildThisFileDirectory)external\mono\external\linker</LinkerSourceDirectory>
diff --git a/build-tools/dependencies/dependencies.projitems b/build-tools/dependencies/dependencies.projitems
index a75e37dbb07..a3046d44919 100644
--- a/build-tools/dependencies/dependencies.projitems
+++ b/build-tools/dependencies/dependencies.projitems
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
-    <_DarwinMonoFramework>MonoFramework-MDK-5.8.0.22.macos10.xamarin.universal.pkg</_DarwinMonoFramework>
+    <_DarwinMonoFramework>MonoFramework-MDK-5.10.0.47.macos10.xamarin.universal.pkg</_DarwinMonoFramework>
     <_AptGetInstall>apt-get -f -u install</_AptGetInstall>
   </PropertyGroup>
   <ItemGroup>
@@ -59,7 +59,7 @@
       <MaximumVersion Condition=" '$(IgnoreMaxMonoVersion)' == '' Or '$(IgnoreMaxMonoVersion)' == 'False' " >$(MonoRequiredMaximumVersion)</MaximumVersion>
       <DarwinMinimumVersion>$(MonoRequiredDarwinMinimumVersion)</DarwinMinimumVersion>
       <CurrentVersionCommand>$(MSBuildThisFileDirectory)..\scripts\mono-version</CurrentVersionCommand>
-      <DarwinMinimumUrl>https://bosstoragemirror.azureedge.net/wrench/mono-2017-10/7e/7e85cfa5d228cd5148e59cde1d4d663457f96966/$(_DarwinMonoFramework)</DarwinMinimumUrl>
+      <DarwinMinimumUrl>https://xamjenkinsartifact.azureedge.net/build-package-osx-mono/2017-12/41/$(_DarwinMonoFramework)</DarwinMinimumUrl>
       <DarwinInstall>installer -pkg "$(AndroidToolchainCacheDirectory)\$(_DarwinMonoFramework)" -target /</DarwinInstall>
     </RequiredProgram>
   </ItemGroup>
diff --git a/build-tools/mono-runtimes/ProfileAssemblies.projitems b/build-tools/mono-runtimes/ProfileAssemblies.projitems
index 1b7740d47e5..957cbf6b368 100644
--- a/build-tools/mono-runtimes/ProfileAssemblies.projitems
+++ b/build-tools/mono-runtimes/ProfileAssemblies.projitems
@@ -260,8 +260,11 @@
     <MonoTestAssembly Include="monodroid_System.Xml.Linq_test.dll">
       <SourcePath>System.Xml.Linq</SourcePath>
     </MonoTestAssembly>
-    <MonoTestAssembly Include="nunitlite.dll">
-      <SourcePath>lib/monodroid</SourcePath>
+    <MonoTestAssembly Include="System.Runtime.CompilerServices.Unsafe.dll">
+      <!-- This is referenced by monodroid_corlib_xunit-test.dll -->
+      <SourcePath>System.Runtime.CompilerServices.Unsafe</SourcePath>
+      <TestType>reference</TestType>
     </MonoTestAssembly>
+    <MonoTestRunner Include="nunitlite.dll" />
   </ItemGroup>
 </Project>
diff --git a/build-tools/mono-runtimes/mono-runtimes.targets b/build-tools/mono-runtimes/mono-runtimes.targets
index 844abd72bea..fcc85be4a08 100644
--- a/build-tools/mono-runtimes/mono-runtimes.targets
+++ b/build-tools/mono-runtimes/mono-runtimes.targets
@@ -57,10 +57,10 @@
     <_BclAssembly Include="@(MonoProfileAssembly)" />
     <_BclExcludeDebugSymbols  Include="System.Windows.dll" />
     <_BclExcludeDebugSymbols  Include="System.Xml.Serialization.dll" />
-    <_BclTestAssemblySource       Include="@(MonoTestAssembly->'$(MonoSourceFullPath)\mcs\class\%(SourcePath)\%(Identity)')" />
-    <_BclTestAssemblySource       Include="@(MonoTestAssembly->'$(MonoSourceFullPath)\mcs\class\%(SourcePath)\%(Filename).pdb')" />
     <_BclTestAssemblyDestination  Include="@(MonoTestAssembly->'$(XAInstallPrefix)\..\..\bcl-tests\%(Identity)')" />
     <_BclTestAssemblyDestination  Include="@(MonoTestAssembly->'$(XAInstallPrefix)\..\..\bcl-tests\%(Filename).pdb')" />
+    <_BclTestAssemblyDestination  Include="@(MonoTestRunner->'$(XAInstallPrefix)\..\..\bcl-tests\%(Identity)')" />
+    <_BclTestAssemblyDestination  Include="@(MonoTestRunner->'$(XAInstallPrefix)\..\..\bcl-tests\%(Filename).pdb')" />
   </ItemGroup>
   <ItemGroup>
     <_BclTestOutput Include="@(_BclTestAssemblyDestination)" />
@@ -335,12 +335,26 @@
         Command="make -C $(MonoSourceFullPath)\mcs\class\%(MonoTestAssembly.SourcePath) xunit-test-local"
         WorkingDirectory="$(MonoSourceFullPath)"
     />
+
+    <ItemGroup>
+      <_BclTestAssemblyReference Include="@(MonoTestAssembly)" Condition="'%(MonoTestAssembly.TestType)' == 'reference'" />
+      <_BclTestAssemblyXUnit  Include="@(MonoTestAssembly)" Condition="'%(MonoTestAssembly.TestType)' == 'xunit'" />
+      <_BclTestAssemblyNUnit  Include="@(MonoTestAssembly)" Condition="'%(MonoTestAssembly.TestType)' == ''" />
+      <_BclTestAssemblySource Include="@(_BclTestAssemblyReference->'$(MonoSourceFullPath)\mcs\class\lib\monodroid\%(Identity)')" />
+      <_BclTestAssemblySource Include="@(_BclTestAssemblyReference->'$(MonoSourceFullPath)\mcs\class\lib\monodroid\%(Filename).pdb')" Condition="Exists('@(_BclTestAssemblyReference->'$(MonoSourceFullPath)\mcs\class\lib\monodroid\%(Filename).pdb')')" />
+      <_BclTestAssemblySource Include="@(_BclTestAssemblyXUnit->'$(MonoSourceFullPath)\mcs\class\%(SourcePath)\%(Identity)')" />
+      <_BclTestAssemblySource Include="@(_BclTestAssemblyXUnit->'$(MonoSourceFullPath)\mcs\class\%(SourcePath)\%(Filename).pdb')" />
+      <_BclTestAssemblySource Include="@(_BclTestAssemblyNUnit->'$(MonoSourceFullPath)\mcs\class\lib\monodroid\tests\%(Identity)')" />
+      <_BclTestAssemblySource Include="@(_BclTestAssemblyNUnit->'$(MonoSourceFullPath)\mcs\class\lib\monodroid\tests\%(Filename).pdb')" />
+      <_BclTestAssemblySource Include="@(MonoTestRunner->'$(MonoSourceFullPath)\mcs\class\lib\monodroid\%(Identity)')" />
+      <_BclTestAssemblySource Include="@(MonoTestRunner->'$(MonoSourceFullPath)\mcs\class\lib\monodroid\%(Filename).pdb')" />
+    </ItemGroup>
     <Copy
         SourceFiles="@(_BclTestAssemblySource)"
-        DestinationFiles="@(_BclTestAssemblyDestination)"
+        DestinationFolder="$(XAInstallPrefix)\..\..\bcl-tests"
     />
     <Touch
-        Files="@(_BclTestAssemblyDestination)"
+        Files="@(_BclTestAssemblySource->'$(XAInstallPrefix)\..\..\bcl-tests\%(Filename)%(Extension)')"
     />
     <ItemGroup>
       <_BclTestContent      Include="$(MonoSourceFullPath)\mcs\class\%(MonoTestAssembly.SourcePath)\Test\**\*.*" />
diff --git a/external/mono b/external/mono
index 3c3e692887a..a0af42ab186 160000
--- a/external/mono
+++ b/external/mono
@@ -1 +1 @@
-Subproject commit 3c3e692887af323549aca938dd6d3dca7a9a6cc8
+Subproject commit a0af42ab186cf997eb7abd8647b4fdc359bcde96
diff --git a/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Build.Tasks.csproj b/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Build.Tasks.csproj
index 6c60361d00f..67b8a26564e 100644
--- a/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Build.Tasks.csproj
+++ b/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Build.Tasks.csproj
@@ -272,99 +272,105 @@
     <Compile Include="Tasks\ReadImportedLibrariesCache.cs" />
     <Compile Include="Utilities\XDocumentExtensions.cs" />
     <Compile Include="Linker\MonoDroid.Tuner\PreserveRuntimeSerialization.cs" />
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker\Annotations.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\Annotations.cs">
       <Link>Linker\Mono.Linker\Annotations.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker\AssemblyAction.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\AssemblyAction.cs">
       <Link>Linker\Mono.Linker\AssemblyAction.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker\AssemblyResolver.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\AssemblyResolver.cs">
       <Link>Linker\Mono.Linker\AssemblyResolver.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker\I18nAssemblies.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\I18nAssemblies.cs">
       <Link>Linker\Mono.Linker\I18nAssemblies.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker\IXApiVisitor.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\IXApiVisitor.cs">
       <Link>Linker\Mono.Linker\IXApiVisitor.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker\LinkContext.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\LinkContext.cs">
       <Link>Linker\Mono.Linker\LinkContext.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker\MethodAction.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\MethodAction.cs">
       <Link>Linker\Mono.Linker\MethodAction.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker\MethodReferenceExtensions.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\MethodReferenceExtensions.cs">
       <Link>Linker\Mono.Linker\MethodReferenceExtensions.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker\Pipeline.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\Pipeline.cs">
       <Link>Linker\Mono.Linker\Pipeline.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker\TypePreserve.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\TypePreserve.cs">
       <Link>Linker\Mono.Linker\TypePreserve.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker\TypeReferenceExtensions.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\TypeReferenceExtensions.cs">
       <Link>Linker\Mono.Linker\TypeReferenceExtensions.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker\XApiReader.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\XApiReader.cs">
       <Link>Linker\Mono.Linker\XApiReader.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker.Steps\BlacklistStep.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker.Steps\BlacklistStep.cs">
       <Link>Linker\Mono.Linker.Steps\BlacklistStep.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker.Steps\BaseStep.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker.Steps\BaseStep.cs">
       <Link>Linker\Mono.Linker.Steps\BaseStep.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker.Steps\CleanStep.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker.Steps\CleanStep.cs">
       <Link>Linker\Mono.Linker.Steps\CleanStep.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker.Steps\IStep.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker.Steps\IStep.cs">
       <Link>Linker\Mono.Linker.Steps\IStep.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker.Steps\LoadI18nAssemblies.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker.Steps\LoadI18nAssemblies.cs">
       <Link>Linker\Mono.Linker.Steps\LoadI18nAssemblies.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker.Steps\LoadReferencesStep.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker.Steps\LoadReferencesStep.cs">
       <Link>Linker\Mono.Linker.Steps\LoadReferencesStep.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker.Steps\OutputStep.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker.Steps\OutputStep.cs">
       <Link>Linker\Mono.Linker.Steps\OutputStep.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker.Steps\RegenerateGuidStep.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker.Steps\RegenerateGuidStep.cs">
       <Link>Linker\Mono.Linker.Steps\RegenerateGuidStep.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker.Steps\ResolveFromAssemblyStep.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker.Steps\ResolveFromAssemblyStep.cs">
       <Link>Linker\Mono.Linker.Steps\ResolveFromAssemblyStep.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker.Steps\ResolveFromXApiStep.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker.Steps\ResolveFromXApiStep.cs">
       <Link>Linker\Mono.Linker.Steps\ResolveFromXApiStep.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker.Steps\ResolveFromXmlStep.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker.Steps\ResolveFromXmlStep.cs">
       <Link>Linker\Mono.Linker.Steps\ResolveFromXmlStep.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker.Steps\ResolveStep.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker.Steps\ResolveStep.cs">
       <Link>Linker\Mono.Linker.Steps\ResolveStep.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker.Steps\TypeMapStep.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker.Steps\TypeMapStep.cs">
       <Link>Linker\Mono.Linker.Steps\TypeMapStep.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker.Steps\SweepStep.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker.Steps\SweepStep.cs">
       <Link>Linker\Mono.Linker.Steps\SweepStep.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker.Steps\MarkStep.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker.Steps\MarkStep.cs">
       <Link>Linker\Mono.Linker.Steps\MarkStep.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker\LoadException.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\LoadException.cs">
       <Link>Linker\Mono.Linker\LoadException.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker\MarkException.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\MarkException.cs">
       <Link>Linker\Mono.Linker\MarkException.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker\ConsoleLogger.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\ConsoleLogger.cs">
       <Link>Linker\Mono.Linker\ConsoleLogger.cs</Link>
     </Compile>
-    <Compile Include="$(LinkerSourceFullPath)\linker\Mono.Linker\ILogger.cs">
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\ILogger.cs">
       <Link>Linker\Mono.Linker\ILogger.cs</Link>
     </Compile>
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\MarkingHelpers.cs">
+      <Link>Linker\Mono.Linker\MarkingHelpers.cs</Link>
+    </Compile>
+    <Compile Include="$(LinkerSourceFullPath)\linker\Linker\Tracer.cs">
+      <Link>Linker\Mono.Linker\Tracer.cs</Link>
+    </Compile>
     <Compile Include="Tasks\MergeResources.cs" />
     <Compile Include="Tasks\GetConvertedJavaLibraries.cs" />
     <Compile Include="Tasks\JavaCompileToolTask.cs" />
diff --git a/tests/BCL-Tests/Xamarin.Android.Bcl-Tests/Xamarin.Android.Bcl-Tests.targets b/tests/BCL-Tests/Xamarin.Android.Bcl-Tests/Xamarin.Android.Bcl-Tests.targets
index 3bc40818051..1b2115baaaf 100644
--- a/tests/BCL-Tests/Xamarin.Android.Bcl-Tests/Xamarin.Android.Bcl-Tests.targets
+++ b/tests/BCL-Tests/Xamarin.Android.Bcl-Tests/Xamarin.Android.Bcl-Tests.targets
@@ -28,8 +28,14 @@
     <Exec
         Command="$(RemapAssemblyRefTool) &quot;%(_Source.Identity)&quot; &quot;$(IntermediateOutputPath)%(_Source.Filename)%(_Source.Extension)&quot; nunitlite &quot;$(_NUnit)&quot;"
     />
+    <ItemGroup>
+      <_DebugSymbol
+          Include="..\..\..\bin\$(Configuration)\bcl-tests\%(MonoTestAssembly.Filename).pdb"
+          Condition="Exists('..\..\..\bin\$(Configuration)\bcl-tests\%(MonoTestAssembly.Filename).pdb')"
+      />
+    </ItemGroup>
     <Copy
-        SourceFiles="..\..\..\bin\$(Configuration)\bcl-tests\%(MonoTestAssembly.Filename).pdb"
+        SourceFiles="@(_DebugSymbol)"
         DestinationFolder="$(IntermediateOutputPath)"
     />
   </Target>