diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ed07c52..78528df 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,6 +13,7 @@ jobs:
       fail-fast: false
       matrix:
         config:
+          - {name: "Ubuntu Clang 20", os: ubuntu-24.04, toolchain: "clang-20", clang_version: 20, installed_clang_version: 17, cmake_args: "-G \"Ninja Multi-Config\" -DCMAKE_CONFIGURATION_TYPES=\"RelWithDebInfo;Asan\" "}
           # Note: clang-19 + Asan setup causes errors on some platforms. Temporary skip some checks via .asan_options.
           - {name: "Ubuntu Clang 19", os: ubuntu-24.04, toolchain: "clang-19", clang_version: 19, installed_clang_version: 17, cmake_args: "-G \"Ninja Multi-Config\" -DCMAKE_CONFIGURATION_TYPES=\"RelWithDebInfo;Asan\" ", asan_options: "new_delete_type_mismatch=0"}
           - {name: "Ubuntu Clang 18", os: ubuntu-24.04, toolchain: "clang-18", clang_version: 18, installed_clang_version: 17, cmake_args: "-G \"Ninja Multi-Config\" -DCMAKE_CONFIGURATION_TYPES=\"RelWithDebInfo;Asan\" "}
diff --git a/CMakePresets.json b/CMakePresets.json
index 3683e7e..a23297c 100644
--- a/CMakePresets.json
+++ b/CMakePresets.json
@@ -45,6 +45,13 @@
       "description": "Build with GCC 12 compilers",
       "toolchainFile": "${sourceDir}/etc/gcc-12-toolchain.cmake"
     },
+    {
+      "name": "clang-20",
+      "inherits": "common",
+      "displayName": "Clang 20",
+      "description": "Build with Clang 20 compilers",
+      "toolchainFile": "${sourceDir}/etc/clang-20-toolchain.cmake"
+    },
     {
       "name": "clang-19",
       "inherits": "common",
@@ -65,6 +72,13 @@
       "displayName": "Clang 17",
       "description": "Build with Clang 17 compilers",
       "toolchainFile": "${sourceDir}/etc/clang-17-toolchain.cmake"
+    },
+    {
+      "name": "clang-16",
+      "inherits": "common",
+      "displayName": "Clang 16",
+      "description": "Build with Clang 16 compilers",
+      "toolchainFile": "${sourceDir}/etc/clang-16-toolchain.cmake"
     }
   ],
   "buildPresets": [
@@ -93,6 +107,11 @@
       "inherits": "common",
       "configurePreset": "gcc-12"
     },
+    {
+      "name": "clang-20",
+      "inherits": "common",
+      "configurePreset": "clang-20"
+    },
     {
       "name": "clang-19",
       "inherits": "common",
@@ -107,6 +126,11 @@
       "name": "clang-17",
       "inherits": "common",
       "configurePreset": "clang-17"
+    },
+    {
+      "name": "clang-16",
+      "inherits": "common",
+      "configurePreset": "clang-16"
     }
   ],
   "testPresets": [
@@ -142,6 +166,11 @@
       "inherits": "common",
       "configurePreset": "gcc-12"
     },
+    {
+      "name": "clang-20",
+      "inherits": "common",
+      "configurePreset": "clang-20"
+    },
     {
       "name": "clang-19",
       "inherits": "common",
@@ -156,6 +185,11 @@
       "name": "clang-17",
       "inherits": "common",
       "configurePreset": "clang-17"
+    },
+    {
+      "name": "clang-16",
+      "inherits": "common",
+      "configurePreset": "clang-16"
     }
   ],
   "workflowPresets": [
@@ -227,6 +261,23 @@
         }
       ]
     },
+    {
+      "name": "clang-20",
+      "steps": [
+        {
+          "type": "configure",
+          "name": "clang-20"
+        },
+        {
+          "type": "build",
+          "name": "clang-20"
+        },
+        {
+          "type": "test",
+          "name": "clang-20"
+        }
+      ]
+    },
     {
       "name": "clang-19",
       "steps": [
@@ -277,6 +328,23 @@
           "name": "clang-17"
         }
       ]
+    },
+    {
+      "name": "clang-16",
+      "steps": [
+        {
+          "type": "configure",
+          "name": "clang-16"
+        },
+        {
+          "type": "build",
+          "name": "clang-16"
+        },
+        {
+          "type": "test",
+          "name": "clang-16"
+        }
+      ]
     }
   ]
 }
diff --git a/README.md b/README.md
index 4a2fcaf..fdedb01 100644
--- a/README.md
+++ b/README.md
@@ -4,6 +4,8 @@
 SPDX-License-Identifier: 2.0 license with LLVM exceptions
 -->
 
+![CI Tests](https://github.com/beman-project/iterator_interface/actions/workflows/ci.yml/badge.svg)
+
 **Implements**:
 * [`std::iterator_interface` (P2727)](https://wg21.link/P2727)
 
diff --git a/etc/clang-20-toolchain.cmake b/etc/clang-20-toolchain.cmake
new file mode 100644
index 0000000..b41013d
--- /dev/null
+++ b/etc/clang-20-toolchain.cmake
@@ -0,0 +1,11 @@
+# cmake-format: off
+# etc/clang-20-toolchain.cmake -*-cmake-*-
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+# cmake-format: on
+
+include_guard(GLOBAL)
+
+set(CMAKE_C_COMPILER clang-20)
+set(CMAKE_CXX_COMPILER clang++-20)
+
+include("${CMAKE_CURRENT_LIST_DIR}/clang-flags.cmake")