diff --git a/Common/File/FileUtil.cpp b/Common/File/FileUtil.cpp
index 62020ee59b..218669cd68 100644
--- a/Common/File/FileUtil.cpp
+++ b/Common/File/FileUtil.cpp
@@ -1068,6 +1068,18 @@ bool CreateEmptyFile(const Path &filename) {
 	return true;
 }
 
+bool IsDirectoryWritable(const Path &path) {
+	// There's no portable way to ask, so just try it and clean up after ourselves.
+	const Path probe = path / ".ppsspp_write_test";
+	FILE *file = OpenCFile(probe, "wb");
+	if (!file) {
+		return false;
+	}
+	fclose(file);
+	Delete(probe, true);
+	return true;
+}
+
 // Deletes an empty directory, returns true on success
 // WARNING: On Android with content URIs, it will delete recursively!
 bool DeleteDir(const Path &path) {
diff --git a/Common/File/FileUtil.h b/Common/File/FileUtil.h
index 054b6c9d33..9b5a0e12cf 100644
--- a/Common/File/FileUtil.h
+++ b/Common/File/FileUtil.h
@@ -123,6 +123,10 @@ bool MoveIfFast(const Path &srcFilename, const Path &destFilename);
 // creates an empty file filename, returns true on success 
 bool CreateEmptyFile(const Path &filename);
 
+// Can we actually create files in this directory? Checks by trying, since permission bits
+// don't tell the whole story (Windows ACLs, read-only mounts, ...).
+bool IsDirectoryWritable(const Path &path);
+
 // Opens ini file (cheats, texture replacements etc.)
 // TODO: Belongs in System or something.
 bool OpenFileInEditor(const Path &fileName);
diff --git a/Core/RetroAchievements.cpp b/Core/RetroAchievements.cpp
index a85f2fc2bf..723252e21a 100644
--- a/Core/RetroAchievements.cpp
+++ b/Core/RetroAchievements.cpp
@@ -37,6 +37,7 @@
 #include "Common/Crypto/md5.h"
 #include "Common/Log.h"
 #include "Common/File/Path.h"
+#include "Common/File/FileUtil.h"
 #include "Common/Net/HTTPRequest.h"
 #include "Common/Net/HTTPClient.h"
 #include "Common/System/OSD.h"
@@ -704,6 +705,21 @@ void InitializeRAIntegration(void *windowHandle) {
 			ERROR_LOG(Log::Achievements, "RAIntegration is enabled, but no main window handle was found.");
 			return;
 		}
+
+		// RAIntegration writes its cache and local achievement data next to the executable. If we
+		// can't write there - the usual case being an install under Program Files - it takes the
+		// emulator down with it as soon as it loads a set, so refuse to load it at all. See #21260.
+		const Path &exeDir = File::GetExeDirectory();
+		if (!File::IsDirectoryWritable(exeDir)) {
+			auto ac = GetI18NCategory(I18NCat::ACHIEVEMENTS);
+			ERROR_LOG(Log::Achievements, "Not loading RAIntegration, '%s' is not writable", exeDir.c_str());
+			g_OSD.Show(OSDType::MESSAGE_ERROR, ac->T("RAIntegrationNotWritable",
+				"RAIntegration needs to write next to PPSSPP.exe, which this install doesn't allow. Use the portable .zip version instead."), "", g_RAImageID, 10.0f);
+			// Carry on without the toolkit - plain achievements still work.
+			TryLoginByToken(true);
+			return;
+		}
+
 		rc_client_begin_load_raintegration(g_rcClient, szFilePath, hWnd, "PPSSPP", PPSSPP_GIT_VERSION, &load_integration_callback, hWnd);
 		return;
 	}
diff --git a/assets/lang/en_US.ini b/assets/lang/en_US.ini
index 5b8dd9a2f0..d0a33db0c3 100644
--- a/assets/lang/en_US.ini
+++ b/assets/lang/en_US.ini
@@ -67,6 +67,7 @@ Missable = Missable
 Notifications = Notifications
 Progression = Progression
 RAIntegration is enabled, but %1 was not found. = RAIntegration is enabled, but %1 was not found.
+RAIntegrationNotWritable = RAIntegration needs to write next to PPSSPP.exe, which this install doesn't allow. Use the portable .zip version instead.
 Recently unlocked = Recently unlocked
 Reconnected to RetroAchievements. = Reconnected to RetroAchievements.
 Register on www.retroachievements.org = Register on www.retroachievements.org