diff --git a/CHANGES b/CHANGES
index 84f657195..5ec6b1903 100644
--- a/CHANGES
+++ b/CHANGES
@@ -2917,3 +2917,5 @@
 * notifications: email notification when cloudron update failed
 * node: update to 22.13.1
 * docker: update to 27.5.1
+* s3: automatically abort old multipart uploads
+
diff --git a/src/backupcleaner.js b/src/backupcleaner.js
index 564485ef3..79dea3e70 100644
--- a/src/backupcleaner.js
+++ b/src/backupcleaner.js
@@ -302,8 +302,11 @@ async function run(progressCallback) {
     await progressCallback({ percent: 70, message: 'Checking storage backend and removing stale entries in database' });
     const missingBackupPaths = await cleanupMissingBackups(backupConfig, progressCallback);
 
-    await progressCallback({ percent: 90, message: 'Cleaning snapshots' });
+    await progressCallback({ percent: 80, message: 'Cleaning snapshots' });
     await cleanupSnapshots(backupConfig);
 
+    await progressCallback({ percent: 80, message: 'Cleaning storage artifacts' });
+    await storage.api(backupConfig.provider).cleanup(backupConfig, progressCallback);
+
     return { removedBoxBackupPaths, removedMailBackupPaths, removedAppBackupPaths, missingBackupPaths };
 }
diff --git a/src/storage/filesystem.js b/src/storage/filesystem.js
index 68af540ea..e0163ccf3 100644
--- a/src/storage/filesystem.js
+++ b/src/storage/filesystem.js
@@ -14,6 +14,8 @@ exports = module.exports = {
     remove,
     removeDir,
 
+    cleanup,
+
     testConfig,
     removePrivateFields,
     injectPrivateFields
@@ -216,6 +218,11 @@ function validateBackupTarget(folder) {
     return null;
 }
 
+async function cleanup(apiConfig, progressCallback) {
+    assert.strictEqual(typeof apiConfig, 'object');
+    assert.strictEqual(typeof progressCallback, 'function');
+}
+
 async function testConfig(apiConfig) {
     assert.strictEqual(typeof apiConfig, 'object');
 
diff --git a/src/storage/gcs.js b/src/storage/gcs.js
index fcaddfcf4..4e50579e4 100644
--- a/src/storage/gcs.js
+++ b/src/storage/gcs.js
@@ -13,6 +13,8 @@ exports = module.exports = {
     remove,
     removeDir,
 
+    cleanup,
+
     testConfig,
     removePrivateFields,
     injectPrivateFields,
@@ -181,6 +183,11 @@ async function removeDir(apiConfig, pathPrefix, progressCallback) {
     progressCallback({ progress: `Deleted ${total} files` });
 }
 
+async function cleanup(apiConfig, progressCallback) {
+    assert.strictEqual(typeof apiConfig, 'object');
+    assert.strictEqual(typeof progressCallback, 'function');
+}
+
 async function testConfig(apiConfig) {
     assert.strictEqual(typeof apiConfig, 'object');
 
diff --git a/src/storage/interface.js b/src/storage/interface.js
index 363e8d0f0..eb43694f0 100644
--- a/src/storage/interface.js
+++ b/src/storage/interface.js
@@ -109,6 +109,14 @@ async function removeDir(apiConfig, pathPrefix, progressCallback) {
     throw new BoxError(BoxError.NOT_IMPLEMENTED, 'removeDir is not implemented');
 }
 
+async function cleanup(apiConfig, progressCallback) {
+    assert.strictEqual(typeof apiConfig, 'object');
+    assert.strictEqual(typeof progressCallback, 'function');
+
+    // Result: none
+    throw new BoxError(BoxError.NOT_IMPLEMENTED, 'cleanup is not implemented');
+}
+
 async function testConfig(apiConfig) {
     assert.strictEqual(typeof apiConfig, 'object');
 
diff --git a/src/storage/noop.js b/src/storage/noop.js
index c970b5bcf..636f3fdbd 100644
--- a/src/storage/noop.js
+++ b/src/storage/noop.js
@@ -13,6 +13,8 @@ exports = module.exports = {
     remove,
     removeDir,
 
+    cleanup,
+
     testConfig,
     removePrivateFields,
     injectPrivateFields
@@ -94,6 +96,11 @@ async function removeDir(apiConfig, pathPrefix, progressCallback) {
     debug(`removeDir: ${pathPrefix}`);
 }
 
+async function cleanup(apiConfig, progressCallback) {
+    assert.strictEqual(typeof apiConfig, 'object');
+    assert.strictEqual(typeof progressCallback, 'function');
+}
+
 async function testConfig(apiConfig) {
     assert.strictEqual(typeof apiConfig, 'object');
 }
diff --git a/src/storage/s3.js b/src/storage/s3.js
index c8de6a852..84b4acfaa 100644
--- a/src/storage/s3.js
+++ b/src/storage/s3.js
@@ -13,6 +13,8 @@ exports = module.exports = {
     remove,
     removeDir,
 
+    cleanup,
+
     testConfig,
     removePrivateFields,
     injectPrivateFields,
@@ -356,7 +358,7 @@ async function copyFile(apiConfig, oldFilePath, newFilePath, entry, progressCall
         uploadedParts[index] = { ETag: part.CopyPartResult.ETag, PartNumber: partCopyParams.PartNumber };
     }));
 
-    if (copyError) { // we must still recommend the user to set a AbortIncompleteMultipartUpload lifecycle rule
+    if (copyError) {
         const abortParams = {
             Bucket: apiConfig.bucket,
             Key: path.join(newFilePath, relativePath),
@@ -480,6 +482,24 @@ async function removeDir(apiConfig, pathPrefix, progressCallback) {
     progressCallback({ message: `Removed ${total} files` });
 }
 
+// often, the AbortIncompleteMultipartUpload lifecycle rule is not added to the bucket resulting in large bucket sizes over time
+async function cleanup(apiConfig, progressCallback) {
+    assert.strictEqual(typeof apiConfig, 'object');
+    assert.strictEqual(typeof progressCallback, 'function');
+
+    const s3 = createS3Client(apiConfig, { retryStrategy: RETRY_STRATEGY });
+
+    const uploads = await s3.listMultipartUploads({ Bucket: apiConfig.bucket, Prefix: apiConfig.prefix });
+    progressCallback({ message: `Cleaning up any aborted multi-part uploads. count:${uploads.Uploads?.length || 0} truncated:${uploads.IsTruncated}` });
+    if (!uploads.Uploads) return;
+
+    for (const upload of uploads.Uploads) {
+        if (Date.now() - new Date(upload.Initiated) < 3 * 24 * 60 * 60 * 1000) continue; // 3 days ago
+        progressCallback({ message: `Cleaning up multi-part upload uploadId:${upload.UploadId} key:${upload.Key}` });
+        await safe(s3.abortMultipartUpload({ Bucket: apiConfig.bucket, Key: upload.Key, UploadId: upload.UploadId }), { debug }); // ignore error
+    }
+}
+
 async function testConfig(apiConfig) {
     assert.strictEqual(typeof apiConfig, 'object');