diff --git a/backend/open_webui/migrations/versions/a0b1c2d3e4f5_add_memory_user_id_index.py b/backend/open_webui/migrations/versions/a0b1c2d3e4f5_add_memory_user_id_index.py
new file mode 100644
index 0000000000..a52ade7711
--- /dev/null
+++ b/backend/open_webui/migrations/versions/a0b1c2d3e4f5_add_memory_user_id_index.py
@@ -0,0 +1,22 @@
+"""Add memory user_id index
+
+Revision ID: a0b1c2d3e4f5
+Revises: 4de81c2a3af1
+Create Date: 2025-09-15 03:00:00.000000
+
+"""
+
+from alembic import op
+
+revision = 'a0b1c2d3e4f5'
+down_revision = '4de81c2a3af1'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.create_index('ix_memory_user_id', 'memory', ['user_id'])
+
+
+def downgrade():
+    op.drop_index('ix_memory_user_id', table_name='memory')
diff --git a/backend/open_webui/models/memories.py b/backend/open_webui/models/memories.py
index e956826800..1ec52eeb6a 100644
--- a/backend/open_webui/models/memories.py
+++ b/backend/open_webui/models/memories.py
@@ -19,7 +19,7 @@ class Memory(Base):
     __tablename__ = 'memory'
 
     id = Column(String, primary_key=True, unique=True)
-    user_id = Column(String)
+    user_id = Column(String, index=True)
     content = Column(Text)
     updated_at = Column(BigInteger)
     created_at = Column(BigInteger)