diff --git a/src/db/migrations/20250519141528_change_fake_feature_flag_user.js b/src/db/migrations/20250519141528_change_fake_feature_flag_user.js
new file mode 100644
index 00000000000..cf12cecd887
--- /dev/null
+++ b/src/db/migrations/20250519141528_change_fake_feature_flag_user.js
@@ -0,0 +1,96 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * @param { import("knex").Knex } knex
+ * @returns { Promise<void> }
+ */
+export async function up(knex) {
+  // Legacy feature flags that were assigned a fake feature flag user
+  // in the feature_flag_events table, were associated with a subscriber
+  // without an FxA UID. Now that we want to delete those subcribers,
+  // the foreign key on this table is blocking it.
+  // Thus, this changes the assciated fake feature flag user to one with
+  // an FxA UID.
+
+  const previousFakeFirstuser = await knex("feature_flag_events")
+    .join(
+      "subscribers",
+      "feature_flag_events.created_by_subscriber_id",
+      "subscribers.id",
+    )
+    .first("created_by_subscriber_id")
+    .whereLike("primary_email", "%@mozilla.com")
+    .andWhere("feature_flag_events.created_at", "<", "2025-03-06");
+  if (!previousFakeFirstuser) {
+    console.log(
+      "No existing feature flag events with fake authors, so nothing to migrate.",
+    );
+    return;
+  }
+
+  const newFakeFirstuser = await knex("subscribers")
+    .select("id")
+    .whereLike("primary_email", "%@mozilla.com")
+    .whereNotNull("fxa_uid")
+    .first();
+  if (!newFakeFirstuser) {
+    throw new Error(
+      "Couldn't find a subscriber with an @mozilla.com email address and an FxA UID to attribute pre-existing feature flags to.",
+    );
+  }
+
+  console.log({ previousFakeFirstuser, newFakeFirstuser });
+  await knex("feature_flag_events")
+    .update("created_by_subscriber_id", newFakeFirstuser.id)
+    .where(
+      "created_by_subscriber_id",
+      previousFakeFirstuser.created_by_subscriber_id,
+    )
+    // We ran the migration `20250225111207_add_feature_flag_events` on March 5th,
+    // so no feature flags should have been assigned to `previousFakeFirstuser` after that date:
+    .andWhere("created_at", "<", "2025-03-06");
+}
+/**
+ * @param { import("knex").Knex } knex
+ * @returns { Promise<void> }
+ */
+export async function down(knex) {
+  const existingFeatureFlagEvents = await knex("feature_flag_events").select(
+    "*",
+  );
+
+  if (existingFeatureFlagEvents.length === 0) {
+    console.log(
+      "No existing feature flag events with fake authors, so nothing to migrate.",
+    );
+    return;
+  }
+
+  const previousFakeFirstuser = await knex("subscribers")
+    .select("id")
+    .whereLike("primary_email", "%@mozilla.com")
+    .first();
+  if (!previousFakeFirstuser) {
+    throw new Error(
+      "Couldn't find a subscriber with an @mozilla.com email address that pre-existing feature flags were attributed to.",
+    );
+  }
+
+  const newFakeFirstuser = await knex("subscribers")
+    .select("id")
+    .whereLike("primary_email", "%@mozilla.com")
+    .whereNotNull("fxa_uid")
+    .first();
+  if (!newFakeFirstuser) {
+    throw new Error(
+      "Couldn't find a subscriber with an @mozilla.com email address and an FxA UID that pre-existing feature flags were attributed to.",
+    );
+  }
+
+  await knex("feature_flag_events")
+    .update("created_by_subscriber_id", previousFakeFirstuser.id)
+    .where("created_by_subscriber_id", newFakeFirstuser.id)
+    .andWhere("created_at", "<", "2025-03-06");
+}