diff --git a/tools/gc-unused-labels.sql b/tools/gc-unused-labels.sql
new file mode 100644
index 0000000..d5c05d0
--- /dev/null
+++ b/tools/gc-unused-labels.sql
@@ -0,0 +1,17 @@
+-- Garbage collect LabelDef rows from all projects where:
+-- 1. The label is not currently in use (it does not join to Issue2Label).
+-- 2. The label is not a well-known label (it does not have a rank).
+-- There are currently about 1500 such labels in the prod database.
+
+CREATE TABLE LabelDefToDelete (id INT);
+
+INSERT INTO LabelDefToDelete (id)
+  SELECT id FROM LabelDef
+    LEFT JOIN Issue2Label ON LabelDef.id = Issue2Label.label_id
+    WHERE issue_id IS NULL
+    AND rank IS NULL;
+
+DELETE FROM LabelDef
+  WHERE id IN (SELECT * FROM LabelDefToDelete)
+  LIMIT 2000;
+