diff --git a/src/builder/CMakeLists.txt b/src/builder/CMakeLists.txt
index 1b1f9a3..8768b0d 100644
--- a/src/builder/CMakeLists.txt
+++ b/src/builder/CMakeLists.txt
@@ -3,6 +3,7 @@ set(CPACK_DEBIAN_BUILDER_PACKAGE_NAME "sai-builder")
 
 set(SRCS
 	b-sai.c
+	b-win32-service.c
 	b-conf.c
 	b-ws-server.c
 	b-nspawn.c
diff --git a/src/builder/b-private.h b/src/builder/b-private.h
index 63ad022..f61c09b 100644
--- a/src/builder/b-private.h
+++ b/src/builder/b-private.h
@@ -320,6 +320,12 @@ suspender_destroy(void);
 int
 saib_reassess_idle_situation(void);
 
+int
+saib_app_run(int argc, const char **argv);
+
+void
+saib_app_stop(void);
+
 #if defined(__APPLE__)
 int
 saib_need_wakelock(void);
diff --git a/src/builder/b-sai.c b/src/builder/b-sai.c
index 38dda21..3f968b8 100644
--- a/src/builder/b-sai.c
+++ b/src/builder/b-sai.c
@@ -424,8 +424,14 @@ sai_ns_destroy(struct sai_nspawn *ns)
 	free(ns);
 }
 
+void saib_app_stop(void)
+{
+	interrupted = 1;
+	lws_cancel_service(builder.context);
+}
 
-int main(int argc, const char **argv)
+int
+saib_app_run(int argc, const char **argv)
 {
 	int logs = LLL_USER | LLL_ERR | LLL_WARN | LLL_NOTICE;
 	struct lws_context_creation_info info;
@@ -664,3 +670,17 @@ bail:
 
 	return 0;
 }
+
+#if defined(WIN32)
+extern int saib_service_run(int argc, const char **argv);
+#endif
+
+int main(int argc, const char **argv)
+{
+#if defined(WIN32)
+	if (lws_cmdline_option(argc, argv, "--service"))
+		return saib_service_run(argc, argv);
+#endif
+
+	return saib_app_run(argc, argv);
+}
diff --git a/src/builder/b-win32-service.c b/src/builder/b-win32-service.c
new file mode 100644
index 0000000..aacab5d
--- /dev/null
+++ b/src/builder/b-win32-service.c
@@ -0,0 +1,151 @@
+/*
+ * sai-builder - Windows Service support
+ *
+ * Copyright (C) 2019 - 2025 Andy Green <andy@warmcat.com>
+ *
+ *  This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Lesser General Public
+ *  License as published by the Free Software Foundation:
+ *  version 2.1 of the License.
+ *
+ *  This library is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  Lesser General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Lesser General Public
+ *  License along with this library; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ *  MA  02110-1301  USA
+ */
+
+#if defined(WIN32)
+
+#include <windows.h>
+#include <tchar.h>
+#include <stdio.h>
+#include "b-private.h"
+
+SERVICE_STATUS        g_ServiceStatus = {0};
+SERVICE_STATUS_HANDLE g_StatusHandle = NULL;
+
+VOID WINAPI ServiceMain(DWORD argc, LPTSTR *argv);
+VOID WINAPI ServiceCtrlHandler(DWORD);
+
+static int g_argc;
+static const char **g_argv;
+
+#define SERVICE_NAME  TEXT("SaiBuilder")
+
+int saib_service_run(int argc, const char **argv)
+{
+    SERVICE_TABLE_ENTRY ServiceTable[] =
+    {
+        {SERVICE_NAME, (LPSERVICE_MAIN_FUNCTION) ServiceMain},
+        {NULL, NULL}
+    };
+
+    /* Capture arguments to pass to the service main */
+    g_argc = argc;
+    g_argv = argv;
+
+    /* This call blocks until the service is stopped */
+    if (StartServiceCtrlDispatcher(ServiceTable) == FALSE)
+    {
+        return GetLastError();
+    }
+
+    return 0;
+}
+
+VOID WINAPI ServiceMain(DWORD argc, LPTSTR *argv)
+{
+    int rc;
+
+    /*
+     * Note on arguments:
+     * argc/argv passed to ServiceMain contain arguments specified in the
+     * "Start parameters" of the Service Control Manager or via "sc start ... args".
+     * These are distinct from the process command line arguments passed to main().
+     *
+     * Typically, a service is configured via its binPath (e.g., "sai-builder.exe --service -c conf").
+     * These arguments are received by main() and captured in g_argc/g_argv.
+     * We use these captured arguments to start the app, ensuring configuration is preserved.
+     */
+
+    g_StatusHandle = RegisterServiceCtrlHandler(SERVICE_NAME, ServiceCtrlHandler);
+
+    if (g_StatusHandle == NULL)
+    {
+        return;
+    }
+
+    ZeroMemory(&g_ServiceStatus, sizeof(g_ServiceStatus));
+    g_ServiceStatus.dwServiceType = SERVICE_WIN32_OWN_PROCESS;
+    g_ServiceStatus.dwControlsAccepted = 0;
+    g_ServiceStatus.dwCurrentState = SERVICE_START_PENDING;
+    g_ServiceStatus.dwWin32ExitCode = 0;
+    g_ServiceStatus.dwServiceSpecificExitCode = 0;
+    g_ServiceStatus.dwCheckPoint = 0;
+
+    if (SetServiceStatus(g_StatusHandle, &g_ServiceStatus) == FALSE)
+    {
+        return;
+    }
+
+    /*
+     * We don't need a separate worker thread because ServiceMain runs in its own thread
+     * and we can block here. However, we need to handle the control requests.
+     */
+
+    g_ServiceStatus.dwControlsAccepted = SERVICE_ACCEPT_STOP;
+    g_ServiceStatus.dwCurrentState = SERVICE_RUNNING;
+    g_ServiceStatus.dwWin32ExitCode = 0;
+    g_ServiceStatus.dwCheckPoint = 0;
+
+    if (SetServiceStatus(g_StatusHandle, &g_ServiceStatus) == FALSE)
+    {
+        return;
+    }
+
+    /* Run the app using the arguments passed to the process */
+    rc = saib_app_run(g_argc, g_argv);
+
+    g_ServiceStatus.dwControlsAccepted = 0;
+    g_ServiceStatus.dwCurrentState = SERVICE_STOPPED;
+
+    if (rc) {
+        g_ServiceStatus.dwWin32ExitCode = ERROR_SERVICE_SPECIFIC_ERROR;
+        g_ServiceStatus.dwServiceSpecificExitCode = (DWORD)rc;
+    } else {
+        g_ServiceStatus.dwWin32ExitCode = 0;
+    }
+
+    g_ServiceStatus.dwCheckPoint = 3;
+
+    SetServiceStatus(g_StatusHandle, &g_ServiceStatus);
+}
+
+VOID WINAPI ServiceCtrlHandler(DWORD CtrlCode)
+{
+    switch (CtrlCode)
+    {
+    case SERVICE_CONTROL_STOP:
+        if (g_ServiceStatus.dwCurrentState != SERVICE_RUNNING)
+            break;
+
+        g_ServiceStatus.dwControlsAccepted = 0;
+        g_ServiceStatus.dwCurrentState = SERVICE_STOP_PENDING;
+        g_ServiceStatus.dwWin32ExitCode = 0;
+        g_ServiceStatus.dwCheckPoint = 4;
+
+        SetServiceStatus(g_StatusHandle, &g_ServiceStatus);
+
+        saib_app_stop();
+        break;
+
+    default:
+        break;
+    }
+}
+#endif