diff --git a/.buckconfig b/.buckconfig
index 603fa928bcb..097057ee6ae 100644
--- a/.buckconfig
+++ b/.buckconfig
@@ -23,7 +23,7 @@
   gh_facebook_buck2_shims_meta = shim
 
 [cxx]
-  cxxflags = -g -std=c++17
+  cxxflags = -g -std=c++20
 
 [parser]
   target_platform_detector_spec = target:root//...->prelude//platforms:default target:shim//...->prelude//platforms:default
diff --git a/CMakeLists.txt b/CMakeLists.txt
index abd032e3e30..5687a2992f1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -110,7 +110,7 @@ include(ExternalProject)
 include(GNUInstallDirs)
 
 if(NOT CMAKE_CXX_STANDARD)
-  set(CMAKE_CXX_STANDARD 17)
+  set(CMAKE_CXX_STANDARD 20)
 endif()
 announce_configured_options(CMAKE_CXX_STANDARD)
 
@@ -233,6 +233,8 @@ endif()
 # they can be properly gc'd. -s: strip symbol.
 if(WIN32)
   set(CMAKE_CXX_FLAGS_RELEASE "/Gy /Gw ${CMAKE_CXX_FLAGS_RELEASE}")
+  # C++20 headers pull in <windows.h>; suppress its min/max macros.
+  add_compile_definitions(NOMINMAX)
 else()
   set(CMAKE_CXX_FLAGS_RELEASE
       "-ffunction-sections -fdata-sections ${CMAKE_CXX_FLAGS_RELEASE}"
diff --git a/backends/arm/CMakeLists.txt b/backends/arm/CMakeLists.txt
index 095ccb6a49b..67f2635275e 100644
--- a/backends/arm/CMakeLists.txt
+++ b/backends/arm/CMakeLists.txt
@@ -7,6 +7,9 @@ project(arm_backend)
 
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
+# Pin to C++17 for embedded toolchain compatibility (not all support C++20).
+set(CMAKE_CXX_STANDARD 17)
+
 # Source root directory for executorch.
 if(NOT EXECUTORCH_ROOT)
   set(EXECUTORCH_ROOT ${CMAKE_CURRENT_SOURCE_DIR}/../..)
diff --git a/backends/cadence/CMakeLists.txt b/backends/cadence/CMakeLists.txt
index f04bda30a69..9a42fd03fba 100644
--- a/backends/cadence/CMakeLists.txt
+++ b/backends/cadence/CMakeLists.txt
@@ -7,9 +7,8 @@
 # Set the minimum required version of CMake for this project.
 cmake_minimum_required(VERSION 3.10)
 
-if(NOT CMAKE_CXX_STANDARD)
-  set(CMAKE_CXX_STANDARD 17)
-endif()
+# Pin to C++17 for embedded toolchain compatibility (not all support C++20).
+set(CMAKE_CXX_STANDARD 17)
 
 # Set the project name.
 project(cadence_backend)
diff --git a/backends/cadence/fusion_g3/operators/CMakeLists.txt b/backends/cadence/fusion_g3/operators/CMakeLists.txt
index a9501c687bb..b5f0b3909dd 100644
--- a/backends/cadence/fusion_g3/operators/CMakeLists.txt
+++ b/backends/cadence/fusion_g3/operators/CMakeLists.txt
@@ -7,9 +7,8 @@
 cmake_minimum_required(VERSION 3.19)
 
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
-if(NOT CMAKE_CXX_STANDARD)
-  set(CMAKE_CXX_STANDARD 17)
-endif()
+# Pin to C++17 for embedded toolchain compatibility (not all support C++20).
+set(CMAKE_CXX_STANDARD 17)
 
 include(${EXECUTORCH_ROOT}/tools/cmake/Utils.cmake)
 include(${EXECUTORCH_ROOT}/tools/cmake/Codegen.cmake)
diff --git a/backends/cadence/generic/operators/CMakeLists.txt b/backends/cadence/generic/operators/CMakeLists.txt
index dbf06e56bee..a004aaf09ea 100644
--- a/backends/cadence/generic/operators/CMakeLists.txt
+++ b/backends/cadence/generic/operators/CMakeLists.txt
@@ -7,9 +7,8 @@
 cmake_minimum_required(VERSION 3.19)
 
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
-if(NOT CMAKE_CXX_STANDARD)
-  set(CMAKE_CXX_STANDARD 17)
-endif()
+# Pin to C++17 for embedded toolchain compatibility (not all support C++20).
+set(CMAKE_CXX_STANDARD 17)
 
 include(${EXECUTORCH_ROOT}/tools/cmake/Utils.cmake)
 include(${EXECUTORCH_ROOT}/tools/cmake/Codegen.cmake)
diff --git a/backends/cadence/hifi/operators/CMakeLists.txt b/backends/cadence/hifi/operators/CMakeLists.txt
index b5801f5d488..15c8b19d37b 100644
--- a/backends/cadence/hifi/operators/CMakeLists.txt
+++ b/backends/cadence/hifi/operators/CMakeLists.txt
@@ -7,9 +7,8 @@
 cmake_minimum_required(VERSION 3.19)
 
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
-if(NOT CMAKE_CXX_STANDARD)
-  set(CMAKE_CXX_STANDARD 17)
-endif()
+# Pin to C++17 for embedded toolchain compatibility (not all support C++20).
+set(CMAKE_CXX_STANDARD 17)
 
 include(${EXECUTORCH_ROOT}/tools/cmake/Utils.cmake)
 include(${EXECUTORCH_ROOT}/tools/cmake/Codegen.cmake)
diff --git a/backends/cadence/vision/operators/CMakeLists.txt b/backends/cadence/vision/operators/CMakeLists.txt
index 38e4f97f841..1e828547ede 100644
--- a/backends/cadence/vision/operators/CMakeLists.txt
+++ b/backends/cadence/vision/operators/CMakeLists.txt
@@ -7,9 +7,8 @@
 cmake_minimum_required(VERSION 3.19)
 
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
-if(NOT CMAKE_CXX_STANDARD)
-  set(CMAKE_CXX_STANDARD 17)
-endif()
+# Pin to C++17 for embedded toolchain compatibility (not all support C++20).
+set(CMAKE_CXX_STANDARD 17)
 
 include(${EXECUTORCH_ROOT}/tools/cmake/Utils.cmake)
 include(${EXECUTORCH_ROOT}/tools/cmake/Codegen.cmake)
diff --git a/backends/cortex_m/CMakeLists.txt b/backends/cortex_m/CMakeLists.txt
index f88a6306fed..5fb91724c7a 100644
--- a/backends/cortex_m/CMakeLists.txt
+++ b/backends/cortex_m/CMakeLists.txt
@@ -8,9 +8,8 @@
 cmake_minimum_required(VERSION 3.19)
 
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
-if(NOT CMAKE_CXX_STANDARD)
-  set(CMAKE_CXX_STANDARD 17)
-endif()
+# Pin to C++17 for embedded toolchain compatibility (not all support C++20).
+set(CMAKE_CXX_STANDARD 17)
 
 # Source root directory for executorch
 if(NOT EXECUTORCH_ROOT)
diff --git a/backends/mediatek/CMakeLists.txt b/backends/mediatek/CMakeLists.txt
index 10c28be0053..cda87c59e9e 100644
--- a/backends/mediatek/CMakeLists.txt
+++ b/backends/mediatek/CMakeLists.txt
@@ -8,6 +8,9 @@
 */
 ]]
 
+# Pin to C++17 for embedded toolchain compatibility (not all support C++20).
+set(CMAKE_CXX_STANDARD 17)
+
 # Let include directory as "executorch/..."
 set(_common_include_directories ${CMAKE_CURRENT_SOURCE_DIR}/../../..)
 
diff --git a/backends/nxp/CMakeLists.txt b/backends/nxp/CMakeLists.txt
index bfc4c046be6..cce18eeaae6 100644
--- a/backends/nxp/CMakeLists.txt
+++ b/backends/nxp/CMakeLists.txt
@@ -3,6 +3,9 @@
 # This source code is licensed under the BSD-style license found in the
 # LICENSE file in the root directory of this source tree.
 
+# Pin to C++17 for embedded toolchain compatibility (not all support C++20).
+set(CMAKE_CXX_STANDARD 17)
+
 set(_common_include_directories ${CMAKE_CURRENT_SOURCE_DIR}/../../..)
 add_compile_definitions(C10_USING_CUSTOM_GENERATED_MACROS)