diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000000..08feed4c94
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1,17 @@
+# Mercury repository line-ending policy.
+#
+# Default: treat all detected text files as text, normalize to LF in the
+# index, and check out with LF in the working tree. This prevents Windows
+# checkouts (with core.autocrlf=true) from injecting CRLF into shell
+# scripts, .mgnuc_opts files, configure scripts, Mercury sources, etc.
+# Shell-script-style consumers (e.g. scripts/mgnuc reading .mgnuc_opts)
+# break when CRLF leaks in, so LF-everywhere is the safe default.
+* text=auto eol=lf
+
+# Binary files: skip all normalization.
+*.png  binary
+*.jpg  binary
+*.jpeg binary
+*.gif  binary
+*.ico  binary
+*.pdf  binary
diff --git a/Documentation/README.MS-VisualC.md b/Documentation/README.MS-VisualC.md
index 5a743f5e2c..6a2fc5c8db 100644
--- a/Documentation/README.MS-VisualC.md
+++ b/Documentation/README.MS-VisualC.md
@@ -4,10 +4,10 @@ Mercury with Microsoft Visual C++
 This file documents the port of Mercury to Windows that uses Microsoft Visual
 C++ (MSVC) as a C compiler.
 
-With MSVC, you can install a Mercury compiler that generates either x86
-(32-bit) or x64 (64-bit) Windows native code in C grades, but not both.
-(You can, of course, have multiple Mercury installations that use MSVC,
-and have one that targets x86 and another that targets x64.)
+With MSVC, you can install a Mercury compiler that generates x86 (32-bit),
+x64 (64-bit), or ARM64 Windows native code in C grades, but only one per
+installation. (You can, of course, have multiple Mercury installations that
+use MSVC, each targeting a different architecture.)
 
 Contents
 --------
@@ -47,13 +47,20 @@ following:
        Start Menu
        └── Visual Studio 2022
            ├── x64 Native Tools Command Prompt for VS 2022
-           └── x86 Native Tools Command Prompt for VS 2022
+           ├── x86 Native Tools Command Prompt for VS 2022
+           └── ARM64 Native Tools Command Prompt for VS 2022
 
-   Select x64 to target 64-bit Windows or x86 to target 32-bit Windows.
+   Select x64 to target 64-bit Windows, x86 to target 32-bit Windows, or
+   ARM64 to target Windows on ARM64.
 
    If you prefer not to use the Start Menu shortcuts, then you can manually set
    up the environment variables by running one of the batch files supplied with
-   Visual Studio (e.g. `vcvars32.bat` for x86, `vcvars64.bat` for x64).
+   Visual Studio (e.g. `vcvars32.bat` for x86, `vcvars64.bat` for x64,
+   `vcvarsarm64.bat` for ARM64).
+
+   To install the ARM64 port, your Visual Studio installation needs the
+   "MSVC v143 - VS 2022 C++ ARM64/ARM64EC build tools" individual component
+   (in addition to "Desktop development with C++").
 
 2. Start the MSYS2 shell using this command:
 
diff --git a/Documentation/README.MSYS2.md b/Documentation/README.MSYS2.md
index 27f7efcb23..e21c2a1d80 100644
--- a/Documentation/README.MSYS2.md
+++ b/Documentation/README.MSYS2.md
@@ -168,6 +168,26 @@ all other MSYS2 environments. A common problem is accidentally using the `MSYS`
 compilers. This happens if you forgot to install the compiler package for your
 specific environment (e.g. `UCRT64`).
 
+### Readline Library
+
+The Mercury debugger (`mdb`) links to GNU readline if `configure` detects it.
+Because the `readline` package shipped in the `MSYS` environment is visible
+on the `PATH` of every other MSYS2 environment, `configure` will detect a
+copy that is not usable for linking from `UCRT64`, `MINGW64`, `MINGW32`,
+`CLANG64` or `CLANGARM64`, and the build will then fail in
+`mercury_trace_readline.c`. To avoid this, either install the readline
+package matching your chosen environment via `pacman`, or pass
+`--without-readline` to `configure`. For example, for `CLANGARM64`:
+
+    pacman -S mingw-w64-clang-aarch64-readline
+
+The corresponding packages for the other environments are
+`mingw-w64-clang-x86_64-readline` (`CLANG64`),
+`mingw-w64-ucrt-x86_64-readline` (`UCRT64`),
+`mingw-w64-x86_64-readline` (`MINGW64`),
+`mingw-w64-i686-readline` (`MINGW32`),
+and `readline` (`MSYS`).
+
 ### Documentation Packages
 
 To build the Mercury documentation, you need the following packages:
diff --git a/NEWS.md b/NEWS.md
index a25187d117..379b7b61df 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1954,8 +1954,9 @@ Changes to the Mercury implementation
 Portability improvements
 ------------------------
 
-* We now support using the 64-bit (i.e. x64) version of Microsoft Visual C++
-  as a C compiler with Mercury.
+* We now support using the 64-bit (x64) and ARM64 versions of Microsoft Visual
+  C++ as a C compiler with Mercury, including building Mercury installations
+  targeting Windows on ARM64.
   See [README.MS-VisualC.md](Documentation/README.MS-VisualC.md) for further
   details.
 
diff --git a/boehm_gc b/boehm_gc
index 79c788493a..cd034c36bc 160000
--- a/boehm_gc
+++ b/boehm_gc
@@ -1 +1 @@
-Subproject commit 79c788493a9365a8265d780ead8f04910739e48f
+Subproject commit cd034c36bc541b17bfd657abe98ceb42c973b848
diff --git a/compiler/check_options.m b/compiler/check_options.m
index a10dd3a917..66e0b4faf2 100644
--- a/compiler/check_options.m
+++ b/compiler/check_options.m
@@ -351,6 +351,7 @@
             "clang",
             "msvc_x86",
             "msvc_x64",
+            "msvc_arm64",
             "unknown"
         ],
         CCTpec =
diff --git a/compiler/compile_target_code.m b/compiler/compile_target_code.m
index d03b998575..4492bbcff7 100644
--- a/compiler/compile_target_code.m
+++ b/compiler/compile_target_code.m
@@ -360,6 +360,7 @@
             % XXX Check whether we need to do anything for these C compilers?
             ( C_CompilerType = cc_cl_x86(_)
             ; C_CompilerType = cc_cl_x64(_)
+            ; C_CompilerType = cc_cl_arm64(_)
             ),
             C_FnAlignOpt = ""
         ;
@@ -496,6 +497,7 @@
     ;
         ( C_CompilerType = cc_cl_x86(_)
         ; C_CompilerType = cc_cl_x64(_)
+        ; C_CompilerType = cc_cl_arm64(_)
         ),
         globals.lookup_accumulating_option(Globals, msvc_flags, FlagsList)
     ;
diff --git a/compiler/globals.m b/compiler/globals.m
index 6474144b14..9b793ceb65 100644
--- a/compiler/globals.m
+++ b/compiler/globals.m
@@ -169,6 +169,7 @@
     ;       cc_clang(maybe(clang_version))
     ;       cc_cl_x86(maybe(int))  % MSVC targeting x86.
     ;       cc_cl_x64(maybe(int))  % MSVC targeting x86_64 (x64).
+    ;       cc_cl_arm64(maybe(int))  % MSVC targeting ARM64 (aarch64).
     ;       cc_unknown.
 
 :- type clang_version
@@ -682,6 +683,7 @@
 convert_c_compiler_type_simple("msvc",     cc_cl_x86(no)).
 convert_c_compiler_type_simple("msvc_x86", cc_cl_x86(no)).
 convert_c_compiler_type_simple("msvc_x64", cc_cl_x64(no)).
+convert_c_compiler_type_simple("msvc_arm64", cc_cl_arm64(no)).
 convert_c_compiler_type_simple("unknown",  cc_unknown).
 
 :- pred convert_c_compiler_type_with_version(string::in, c_compiler_type::out)
@@ -701,6 +703,8 @@
         convert_msvc_x86_version(Version, C_CompilerType)
     else if Tokens = ["msvc", "x64", Version] then
         convert_msvc_x64_version(Version, C_CompilerType)
+    else if Tokens = ["msvc", "arm64", Version] then
+        convert_msvc_arm64_version(Version, C_CompilerType)
     else
         false
     ).
@@ -798,6 +802,13 @@
     Version > 0,
     C_CompilerType = cc_cl_x64(yes(Version)).
 
+:- pred convert_msvc_arm64_version(string::in, c_compiler_type::out) is semidet.
+
+convert_msvc_arm64_version(VersionStr, C_CompilerType) :-
+    string.to_int(VersionStr, Version),
+    Version > 0,
+    C_CompilerType = cc_cl_arm64(yes(Version)).
+
 convert_csharp_compiler_type("microsoft", csharp_microsoft).
 convert_csharp_compiler_type("mono", csharp_mono).
 convert_csharp_compiler_type("unknown", csharp_unknown).
diff --git a/compiler/link_target_code.m b/compiler/link_target_code.m
index 34d42e8c10..4a23912dd7 100644
--- a/compiler/link_target_code.m
+++ b/compiler/link_target_code.m
@@ -619,6 +619,7 @@
         ;
             ( C_CompilerType = cc_cl_x86(_)
             ; C_CompilerType = cc_cl_x64(_)
+            ; C_CompilerType = cc_cl_arm64(_)
             ),
             string.format("-stack:%d", [i(ReserveStackSize)], Flags)
         )
@@ -959,6 +960,18 @@
                 ],
                 join_string_list(RestrictedCmdLinkFlags, "", "", " ",
                     RestrictedCmdLinkOpts)
+            ;
+                C_CompilerType = cc_cl_arm64(_),
+                RestrictedCmdLinkFlags = [
+                    "-nologo",
+                    "-ignore:4001",
+                    "-subsystem:console",
+                    "-machine:arm64",
+                    "-entry:wmainCRTStartup",
+                    "-defaultlib:libcmt"
+                ],
+                join_string_list(RestrictedCmdLinkFlags, "", "", " ",
+                    RestrictedCmdLinkOpts)
             ;
                 ( C_CompilerType = cc_gcc(_, _, _)
                 ; C_CompilerType = cc_clang(_)
@@ -1076,6 +1089,7 @@
     (
         ( C_CompilerType = cc_cl_x86(_)
         ; C_CompilerType = cc_cl_x64(_)
+        ; C_CompilerType = cc_cl_arm64(_)
         ),
         ( if LinkedTargetType = executable then
             % NOTE: -Fe _must not_ be separated from its argument by any
@@ -1211,6 +1225,7 @@
         % lib tool.
         ( C_CompilerType = cc_cl_x86(_)
         ; C_CompilerType = cc_cl_x64(_)
+        ; C_CompilerType = cc_cl_arm64(_)
         ),
         ArOutputSpace = ""
     ;
@@ -1674,6 +1689,7 @@
         ;
             ( CCompilerType = cc_cl_x86(_)
             ; CCompilerType = cc_cl_x64(_)
+            ; CCompilerType = cc_cl_arm64(_)
             ),
             LinkOpt = "",
             LibSuffix = ".lib"
diff --git a/compiler/options.m b/compiler/options.m
index 6dc5ce15b8..7f2cb7da85 100644
--- a/compiler/options.m
+++ b/compiler/options.m
@@ -4573,7 +4573,7 @@
         w("Specify which C compiler to use.")])).
 optdb(oc_target_c,  c_compiler_type,                   string("gcc"),
     priv_arg_help("c-compiler-type",
-        "{gcc,clang,msvc_x86,msvc_x64,unknown}", [])).
+        "{gcc,clang,msvc_x86,msvc_x64,msvc_arm64,unknown}", [])).
     % The `mmc' script will override the default with a value
     % determined at configuration time for the above two options.
     % XXX That argues for this option being oc_config.
diff --git a/configure.ac b/configure.ac
index 0486fa4271..04de2ed04b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -189,7 +189,7 @@ case "$mercury_cv_cc_type" in
         C_COMPILER_TYPE="gcc_${mercury_cv_gcc_version}"
         ;;
 
-    msvc_x86|msvc_x64)
+    msvc_x86|msvc_x64|msvc_arm64)
         MERCURY_HAVE_MSVC=yes
         MERCURY_MSVC_VERSION
         C_COMPILER_TYPE="${mercury_cv_cc_type}_${mercury_cv_msvc_version}"
@@ -206,6 +206,7 @@ esac
 
 case "$mercury_cv_cc_type" in
     msvc_x64) BOEHM_WINDOWS_CPU_TYPE="x64" ;;
+    msvc_arm64) BOEHM_WINDOWS_CPU_TYPE="ARM64" ;;
     *) BOEHM_WINDOWS_CPU_TYPE="x86" ;;
 esac
 
diff --git a/m4/mercury.m4 b/m4/mercury.m4
index faf5978b05..93b90a67fb 100644
--- a/m4/mercury.m4
+++ b/m4/mercury.m4
@@ -642,6 +642,8 @@ int main(int argc, char **argv)
           printf("msvc_x86");
        #elif defined(_M_X64)
           printf("msvc_x64");
+       #elif defined(_M_ARM64)
+          printf("msvc_arm64");
        #else
           printf("unknown");
        #endif
diff --git a/tests/warnings/help_text.err_exp b/tests/warnings/help_text.err_exp
index 3ce30f1116..bec6909ad5 100644
--- a/tests/warnings/help_text.err_exp
+++ b/tests/warnings/help_text.err_exp
@@ -2650,7 +2650,7 @@ Options for target language compilation
         Specify which C compiler to use.
 
     PRIVATE OPTION
-    --c-compiler-type {gcc,clang,msvc_x86,msvc_x64,unknown}
+    --c-compiler-type {gcc,clang,msvc_x86,msvc_x64,msvc_arm64,unknown}
         There is no help text available.
 
     --c-optimize