diff --git a/backfill_is_archived.py b/backfill_is_archived.py
new file mode 100644
index 0000000..33cc66a
--- /dev/null
+++ b/backfill_is_archived.py
@@ -0,0 +1,61 @@
+#!/usr/bin/env python3
+"""
+One-off script to backfill is_archived field on all projects in Firestore.
+
+This sets is_archived = True for projects where phase_name == "Archived",
+and is_archived = False for all other projects.
+
+Usage:
+    python backfill_is_archived.py
+"""
+
+import os
+from firebase_admin import credentials, initialize_app, firestore
+
+# Path to your staging service account JSON
+CREDENTIALS_PATH = "./rothbard-staging2-12345-firebase-adminsdk-fbsvc-7f95268383.json"
+
+def main():
+    # Initialize Firebase Admin with staging credentials
+    cred = credentials.Certificate(CREDENTIALS_PATH)
+    app = initialize_app(cred, name='backfill-is-archived')
+    db = firestore.client(app=app)
+
+    projects_ref = db.collection("projects")
+    docs = list(projects_ref.stream())
+
+    total = len(docs)
+    archived_count = 0
+    updated_count = 0
+    batch_size = 500
+
+    print(f"Found {total} projects. Processing in batches of {batch_size}...")
+
+    for i in range(0, total, batch_size):
+        batch = db.batch()
+        batch_docs = docs[i:i + batch_size]
+
+        for doc in batch_docs:
+            data = doc.to_dict()
+            phase_name = data.get("phase_name", "")
+            is_archived = (phase_name == "Archived")
+
+            if is_archived:
+                archived_count += 1
+
+            # Only update if the field is missing or different
+            if data.get("is_archived") != is_archived:
+                ref = projects_ref.document(doc.id)
+                batch.update(ref, {"is_archived": is_archived})
+                updated_count += 1
+
+        batch.commit()
+        print(f"  Committed batch {i//batch_size + 1}/{(total + batch_size - 1)//batch_size}")
+
+    print(f"\nDone!")
+    print(f"  Total projects: {total}")
+    print(f"  Projects with phase_name == 'Archived': {archived_count}")
+    print(f"  Documents updated: {updated_count}")
+
+if __name__ == "__main__":
+    main()