diff --git a/backend/alembic/versions/f11b408e39d3_force_lowercase_all_users.py b/backend/alembic/versions/f11b408e39d3_force_lowercase_all_users.py
new file mode 100644
index 000000000..48684ea88
--- /dev/null
+++ b/backend/alembic/versions/f11b408e39d3_force_lowercase_all_users.py
@@ -0,0 +1,36 @@
+"""force lowercase all users
+
+Revision ID: f11b408e39d3
+Revises: 3bd4c84fe72f
+Create Date: 2025-02-26 17:04:55.683500
+
+"""
+
+
+# revision identifiers, used by Alembic.
+revision = "f11b408e39d3"
+down_revision = "3bd4c84fe72f"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    # 1) Convert all existing user emails to lowercase
+    from alembic import op
+
+    op.execute(
+        """
+        UPDATE "user"
+        SET email = LOWER(email)
+        """
+    )
+
+    # 2) Add a check constraint to ensure emails are always lowercase
+    op.create_check_constraint("ensure_lowercase_email", "user", "email = LOWER(email)")
+
+
+def downgrade() -> None:
+    # Drop the check constraint
+    from alembic import op
+
+    op.drop_constraint("ensure_lowercase_email", "user", type_="check")
diff --git a/backend/alembic_tenants/versions/34e3630c7f32_lowercase_multi_tenant_user_auth.py b/backend/alembic_tenants/versions/34e3630c7f32_lowercase_multi_tenant_user_auth.py
new file mode 100644
index 000000000..c98fc2ca2
--- /dev/null
+++ b/backend/alembic_tenants/versions/34e3630c7f32_lowercase_multi_tenant_user_auth.py
@@ -0,0 +1,42 @@
+"""lowercase multi-tenant user auth
+
+Revision ID: 34e3630c7f32
+Revises: a4f6ee863c47
+Create Date: 2025-02-26 15:03:01.211894
+
+"""
+from alembic import op
+
+
+# revision identifiers, used by Alembic.
+revision = "34e3630c7f32"
+down_revision = "a4f6ee863c47"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    # 1) Convert all existing rows to lowercase
+    op.execute(
+        """
+        UPDATE user_tenant_mapping
+        SET email = LOWER(email)
+        """
+    )
+    # 2) Add a check constraint so that emails cannot be written in uppercase
+    op.create_check_constraint(
+        "ensure_lowercase_email",
+        "user_tenant_mapping",
+        "email = LOWER(email)",
+        schema="public",
+    )
+
+
+def downgrade() -> None:
+    # Drop the check constraint
+    op.drop_constraint(
+        "ensure_lowercase_email",
+        "user_tenant_mapping",
+        schema="public",
+        type_="check",
+    )
diff --git a/backend/onyx/db/models.py b/backend/onyx/db/models.py
index 0001ec318..6c6eadcb8 100644
--- a/backend/onyx/db/models.py
+++ b/backend/onyx/db/models.py
@@ -7,6 +7,7 @@ from typing import Optional
 from uuid import uuid4
 
 from pydantic import BaseModel
+from sqlalchemy.orm import validates
 from typing_extensions import TypedDict  # noreorder
 from uuid import UUID
 
@@ -206,6 +207,10 @@ class User(SQLAlchemyBaseUserTableUUID, Base):
         primaryjoin="User.id == foreign(ConnectorCredentialPair.creator_id)",
     )
 
+    @validates("email")
+    def validate_email(self, key: str, value: str) -> str:
+        return value.lower() if value else value
+
     @property
     def password_configured(self) -> bool:
         """
@@ -2270,6 +2275,10 @@ class UserTenantMapping(Base):
     email: Mapped[str] = mapped_column(String, nullable=False, primary_key=True)
     tenant_id: Mapped[str] = mapped_column(String, nullable=False)
 
+    @validates("email")
+    def validate_email(self, key: str, value: str) -> str:
+        return value.lower() if value else value
+
 
 # This is a mapping from tenant IDs to anonymous user paths
 class TenantAnonymousUserPath(Base):
diff --git a/web/src/app/auth/login/EmailPasswordForm.tsx b/web/src/app/auth/login/EmailPasswordForm.tsx
index 6f7a48cc9..68e1d2154 100644
--- a/web/src/app/auth/login/EmailPasswordForm.tsx
+++ b/web/src/app/auth/login/EmailPasswordForm.tsx
@@ -36,11 +36,14 @@ export function EmailPasswordForm({
       {popup}
       <Formik
         initialValues={{
-          email: defaultEmail || "",
+          email: defaultEmail ? defaultEmail.toLowerCase() : "",
           password: "",
         }}
         validationSchema={Yup.object().shape({
-          email: Yup.string().email().required(),
+          email: Yup.string()
+            .email()
+            .required()
+            .transform((value) => value.toLowerCase()),
           password: Yup.string().required(),
         })}
         onSubmit={async (values) => {