diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8999f1b925f..b49b2b33e1c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -48,6 +48,15 @@ elseif(VCLIBS_TARGET_ARCHITECTURE MATCHES "^[aA][rR][mM]64$")
     add_compile_definitions(_ARM64_ _VCRT_WIN32_WINNT=0x0A00 _STL_WIN32_WINNT=0x0A00
         _WIN32_WINNT=0x0A00 NTDDI_VERSION=NTDDI_WIN10)
     string(APPEND CMAKE_CXX_STANDARD_LIBRARIES " Synchronization.lib")
+elseif(VCLIBS_TARGET_ARCHITECTURE MATCHES "^[aA][rR][mM]64[eE][cC]")
+    set(VCLIBS_TARGET_ARCHITECTURE "arm64EC")
+    set(VCLIBS_I386_OR_AMD64 "arm64EC")
+    set(VCLIBS_X86_OR_X64 "arm64")
+    add_compile_definitions(_ARM64_ _VCRT_WIN32_WINNT=0x0A00 _STL_WIN32_WINNT=0x0A00
+        _WIN32_WINNT=0x0A00 NTDDI_VERSION=NTDDI_WIN10)
+    string(APPEND CMAKE_CXX_STANDARD_LIBRARIES " Synchronization.lib")
+    add_compile_options(/arm64EC)
+    add_link_options(/machine:arm64ec)
 else()
     message(FATAL_ERROR "Could not determine target architecture: VCLIBS_TARGET_ARCHITECTURE: ${VCLIBS_TARGET_ARCHITECTURE}")
 endif()
diff --git a/azure-devops/cross-build.yml b/azure-devops/cross-build.yml
index 0083c39462d..1a7614a68a9 100644
--- a/azure-devops/cross-build.yml
+++ b/azure-devops/cross-build.yml
@@ -38,7 +38,7 @@ jobs:
       targetPlatform: ${{ parameters.targetPlatform }}
       hostArch: ${{ parameters.hostArch }}
       targetArch: ${{ parameters.vsDevCmdArch }}
-      cmakeAdditionalFlags: '-DTESTS_BUILD_ONLY=ON'
+      cmakeAdditionalFlags: '-DTESTS_BUILD_ONLY=ON -DVCLIBS_TARGET_ARCHITECTURE=${{ parameters.targetPlatform }}'
   - template: run-tests.yml
     parameters:
       hostArch: ${{ parameters.hostArch }}
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index bc5c06b347e..38ea5a6359e 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -82,7 +82,7 @@ stages:
     jobs:
       - template: azure-devops/cross-build.yml
         parameters:
-          targetPlatform: arm
+          targetPlatform: armv7
           vsDevCmdArch: arm
 
   - stage: Build_ARM64
@@ -93,3 +93,12 @@ stages:
         parameters:
           targetPlatform: arm64
           vsDevCmdArch: arm64
+
+  - stage: Build_ARM64EC
+    dependsOn: Build_And_Test_x64
+    displayName: 'Build'
+    jobs:
+      - template: azure-devops/cross-build.yml
+        parameters:
+          targetPlatform: arm64EC
+          vsDevCmdArch: arm64
diff --git a/stl/CMakeLists.txt b/stl/CMakeLists.txt
index 82d2d1e9707..793925a55e8 100644
--- a/stl/CMakeLists.txt
+++ b/stl/CMakeLists.txt
@@ -534,7 +534,7 @@ function(add_stl_dlls D_SUFFIX THIS_CONFIG_DEFINITIONS THIS_CONFIG_COMPILE_OPTIO
     add_library(msvcp${D_SUFFIX}_implib STATIC ${HEADERS})
     target_link_libraries(msvcp${D_SUFFIX}_implib msvcp${D_SUFFIX}_implib_objects)
     add_dependencies(msvcp${D_SUFFIX}_implib msvcp${D_SUFFIX} msvcp_1${D_SUFFIX} msvcp_2${D_SUFFIX} msvcp${D_SUFFIX}_atomic_wait msvcp${D_SUFFIX}_codecvt_ids)
-    set_target_properties(msvcp${D_SUFFIX}_implib PROPERTIES STATIC_LIBRARY_OPTIONS "/NOLOGO;/NODEFAULTLIB;/IGNORE:4006;$<TARGET_LINKER_FILE:msvcp${D_SUFFIX}>;$<TARGET_LINKER_FILE:msvcp_1${D_SUFFIX}>;$<TARGET_LINKER_FILE:msvcp_2${D_SUFFIX}>;$<TARGET_LINKER_FILE:msvcp${D_SUFFIX}_codecvt_ids>;$<TARGET_LINKER_FILE:msvcp${D_SUFFIX}_atomic_wait>")
+    set_target_properties(msvcp${D_SUFFIX}_implib PROPERTIES STATIC_LIBRARY_OPTIONS "/NOLOGO;/NODEFAULTLIB;/IGNORE:4006;$<TARGET_LINKER_FILE:msvcp${D_SUFFIX}>;$<TARGET_LINKER_FILE:msvcp_1${D_SUFFIX}>;$<TARGET_LINKER_FILE:msvcp_2${D_SUFFIX}>;$<TARGET_LINKER_FILE:msvcp${D_SUFFIX}_codecvt_ids>;$<TARGET_LINKER_FILE:msvcp${D_SUFFIX}_atomic_wait>;/machine:${VCLIBS_TARGET_ARCHITECTURE}")
     set_target_properties(msvcp${D_SUFFIX}_implib PROPERTIES ARCHIVE_OUTPUT_NAME "msvcprt${D_SUFFIX}")
 endfunction()
 
@@ -545,11 +545,13 @@ function(add_stl_statics FLAVOR_SUFFIX THIS_CONFIG_DEFINITIONS THIS_CONFIG_COMPI
     add_library(libcpmt${FLAVOR_SUFFIX}_eha OBJECT ${EHA_SOURCES})
     target_compile_definitions(libcpmt${FLAVOR_SUFFIX}_eha PRIVATE "${THIS_CONFIG_DEFINITIONS};_ANNOTATE_VECTOR")
     target_compile_options(libcpmt${FLAVOR_SUFFIX}_eha PRIVATE "${THIS_CONFIG_COMPILE_OPTIONS};/EHa")
+    set_target_properties(libcpmt${FLAVOR_SUFFIX}_eha PROPERTIES STATIC_LIBRARY_OPTIONS "/machine:${VCLIBS_TARGET_ARCHITECTURE}")
 
     add_library(libcpmt${FLAVOR_SUFFIX} STATIC ${HEADERS} ${IMPLIB_SOURCES} ${SOURCES} ${INITIALIZER_SOURCES} ${STATIC_SOURCES})
     target_compile_definitions(libcpmt${FLAVOR_SUFFIX} PRIVATE "${THIS_CONFIG_DEFINITIONS};_ANNOTATE_VECTOR")
     target_compile_options(libcpmt${FLAVOR_SUFFIX} PRIVATE "${THIS_CONFIG_COMPILE_OPTIONS};/EHsc")
     target_link_libraries(libcpmt${FLAVOR_SUFFIX} PRIVATE Boost::math libcpmt${FLAVOR_SUFFIX}_eha)
+    set_target_properties(libcpmt${FLAVOR_SUFFIX} PROPERTIES STATIC_LIBRARY_OPTIONS "/machine:${VCLIBS_TARGET_ARCHITECTURE}")
 endfunction()
 
 add_stl_statics("" "_ITERATOR_DEBUG_LEVEL=0" "${VCLIBS_RELEASE_OPTIONS}")
@@ -559,3 +561,4 @@ add_stl_statics("d1" "_DEBUG;_ITERATOR_DEBUG_LEVEL=1" "${VCLIBS_DEBUG_OPTIONS}")
 add_stl_statics("d0" "_DEBUG;_ITERATOR_DEBUG_LEVEL=0" "${VCLIBS_DEBUG_OPTIONS}")
 
 add_library(stl_asan STATIC ${ASAN_SOURCES})
+set_target_properties(stl_asan PROPERTIES STATIC_LIBRARY_OPTIONS "/machine:${VCLIBS_TARGET_ARCHITECTURE}")
diff --git a/stl/src/vector_algorithms.cpp b/stl/src/vector_algorithms.cpp
index bfce5924326..372a4246971 100644
--- a/stl/src/vector_algorithms.cpp
+++ b/stl/src/vector_algorithms.cpp
@@ -39,6 +39,7 @@ static void _Reverse_copy_tail(_BidIt _First, _BidIt _Last, _OutIt _Dest) noexce
     }
 }
 
+#if !defined(_M_ARM64EC)
 static size_t _Byte_length(const void* _First, const void* _Last) noexcept {
     return static_cast<const unsigned char*>(_Last) - static_cast<const unsigned char*>(_First);
 }
@@ -50,6 +51,7 @@ static void _Advance_bytes(void*& _Target, ptrdiff_t _Offset) noexcept {
 static void _Advance_bytes(const void*& _Target, ptrdiff_t _Offset) noexcept {
     _Target = static_cast<const unsigned char*>(_Target) + _Offset;
 }
+#endif // !defined(_M_ARM64EC)
 
 extern "C" {
 __declspec(noalias) void __cdecl __std_swap_ranges_trivially_swappable_noalias(
@@ -68,7 +70,6 @@ __declspec(noalias) void __cdecl __std_swap_ranges_trivially_swappable_noalias(
             _Advance_bytes(_First2, 32);
         } while (_First1 != _Stop_at);
     }
-#endif // !defined(_M_ARM64EC)
 
     constexpr size_t _Mask_16 = ~((static_cast<size_t>(1) << 4) - 1);
     if (_Byte_length(_First1, _Last1) >= 16
@@ -119,6 +120,7 @@ __declspec(noalias) void __cdecl __std_swap_ranges_trivially_swappable_noalias(
 #else
 #error Unsupported architecture
 #endif
+#endif // !defined(_M_ARM64EC)
 
     auto _First1c = static_cast<unsigned char*>(_First1);
     auto _Last1c  = static_cast<unsigned char*>(_Last1);
@@ -159,7 +161,6 @@ __declspec(noalias) void __cdecl __std_reverse_trivially_swappable_1(void* _Firs
             _Advance_bytes(_First, 32);
         } while (_First != _Stop_at);
     }
-#endif // !defined(_M_ARM64EC)
 
     if (_Byte_length(_First, _Last) >= 32 && _bittest(&__isa_enabled, __ISA_AVAILABLE_SSE42)) {
         const __m128i _Reverse_char_sse = _mm_set_epi8(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
@@ -176,6 +177,7 @@ __declspec(noalias) void __cdecl __std_reverse_trivially_swappable_1(void* _Firs
             _Advance_bytes(_First, 16);
         } while (_First != _Stop_at);
     }
+#endif // !defined(_M_ARM64EC)
 
     _Reverse_tail(static_cast<unsigned char*>(_First), static_cast<unsigned char*>(_Last));
 }
@@ -201,7 +203,6 @@ __declspec(noalias) void __cdecl __std_reverse_trivially_swappable_2(void* _Firs
             _Advance_bytes(_First, 32);
         } while (_First != _Stop_at);
     }
-#endif // !defined(_M_ARM64EC)
 
     if (_Byte_length(_First, _Last) >= 32 && _bittest(&__isa_enabled, __ISA_AVAILABLE_SSE42)) {
         const __m128i _Reverse_short_sse = _mm_set_epi8(1, 0, 3, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14);
@@ -218,6 +219,7 @@ __declspec(noalias) void __cdecl __std_reverse_trivially_swappable_2(void* _Firs
             _Advance_bytes(_First, 16);
         } while (_First != _Stop_at);
     }
+#endif // !defined(_M_ARM64EC)
 
     _Reverse_tail(static_cast<unsigned short*>(_First), static_cast<unsigned short*>(_Last));
 }
@@ -240,7 +242,6 @@ __declspec(noalias) void __cdecl __std_reverse_trivially_swappable_4(void* _Firs
             _Advance_bytes(_First, 32);
         } while (_First != _Stop_at);
     }
-#endif // !defined(_M_ARM64EC)
 
     if (_Byte_length(_First, _Last) >= 32
 #ifdef _M_IX86
@@ -260,6 +261,7 @@ __declspec(noalias) void __cdecl __std_reverse_trivially_swappable_4(void* _Firs
             _Advance_bytes(_First, 16);
         } while (_First != _Stop_at);
     }
+#endif // !defined(_M_ARM64EC)
 
     _Reverse_tail(static_cast<unsigned long*>(_First), static_cast<unsigned long*>(_Last));
 }
@@ -280,7 +282,6 @@ __declspec(noalias) void __cdecl __std_reverse_trivially_swappable_8(void* _Firs
             _Advance_bytes(_First, 32);
         } while (_First != _Stop_at);
     }
-#endif // !defined(_M_ARM64EC)
 
     if (_Byte_length(_First, _Last) >= 32
 #ifdef _M_IX86
@@ -301,6 +302,7 @@ __declspec(noalias) void __cdecl __std_reverse_trivially_swappable_8(void* _Firs
         } while (_First != _Stop_at);
     }
 
+#endif // !defined(_M_ARM64EC)
     _Reverse_tail(static_cast<unsigned long long*>(_First), static_cast<unsigned long long*>(_Last));
 }
 
@@ -322,7 +324,6 @@ __declspec(noalias) void __cdecl __std_reverse_copy_trivially_copyable_1(
             _Advance_bytes(_Dest, 32);
         } while (_Dest != _Stop_at);
     }
-#endif // !defined(_M_ARM64EC)
 
     if (_Byte_length(_First, _Last) >= 16 && _bittest(&__isa_enabled, __ISA_AVAILABLE_SSE42)) {
         const __m128i _Reverse_char_sse = _mm_set_epi8(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
@@ -336,6 +337,7 @@ __declspec(noalias) void __cdecl __std_reverse_copy_trivially_copyable_1(
             _Advance_bytes(_Dest, 16);
         } while (_Dest != _Stop_at);
     }
+#endif // !defined(_M_ARM64EC)
 
     _Reverse_copy_tail(static_cast<const unsigned char*>(_First), static_cast<const unsigned char*>(_Last),
         static_cast<unsigned char*>(_Dest));
@@ -359,7 +361,6 @@ __declspec(noalias) void __cdecl __std_reverse_copy_trivially_copyable_2(
             _Advance_bytes(_Dest, 32);
         } while (_Dest != _Stop_at);
     }
-#endif // !defined(_M_ARM64EC)
 
     if (_Byte_length(_First, _Last) >= 16 && _bittest(&__isa_enabled, __ISA_AVAILABLE_SSE42)) {
         const __m128i _Reverse_short_sse = _mm_set_epi8(1, 0, 3, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14);
@@ -373,6 +374,7 @@ __declspec(noalias) void __cdecl __std_reverse_copy_trivially_copyable_2(
             _Advance_bytes(_Dest, 16);
         } while (_Dest != _Stop_at);
     }
+#endif // !defined(_M_ARM64EC)
 
     _Reverse_copy_tail(static_cast<const unsigned short*>(_First), static_cast<const unsigned short*>(_Last),
         static_cast<unsigned short*>(_Dest));
@@ -393,7 +395,6 @@ __declspec(noalias) void __cdecl __std_reverse_copy_trivially_copyable_4(
             _Advance_bytes(_Dest, 32);
         } while (_Dest != _Stop_at);
     }
-#endif // !defined(_M_ARM64EC)
 
     if (_Byte_length(_First, _Last) >= 16
 #ifdef _M_IX86
@@ -410,6 +411,7 @@ __declspec(noalias) void __cdecl __std_reverse_copy_trivially_copyable_4(
             _Advance_bytes(_Dest, 16);
         } while (_Dest != _Stop_at);
     }
+#endif // !defined(_M_ARM64EC)
 
     _Reverse_copy_tail(static_cast<const unsigned long*>(_First), static_cast<const unsigned long*>(_Last),
         static_cast<unsigned long*>(_Dest));
@@ -429,7 +431,6 @@ __declspec(noalias) void __cdecl __std_reverse_copy_trivially_copyable_8(
             _Advance_bytes(_Dest, 32);
         } while (_Dest != _Stop_at);
     }
-#endif // !defined(_M_ARM64EC)
 
     if (_Byte_length(_First, _Last) >= 16
 #ifdef _M_IX86
@@ -446,6 +447,7 @@ __declspec(noalias) void __cdecl __std_reverse_copy_trivially_copyable_8(
             _Advance_bytes(_Dest, 16);
         } while (_Dest != _Stop_at);
     }
+#endif // !defined(_M_ARM64EC)
 
     _Reverse_copy_tail(static_cast<const unsigned long long*>(_First), static_cast<const unsigned long long*>(_Last),
         static_cast<unsigned long long*>(_Dest));