A side airbag for use in a vehicle includes a main chamber extending along a ceiling of the vehicle and configured to restrain a head of a vehicle occupant when the airbag is deployed. The main chamber includes an inboard panel and an outboard panel that are joined together. The airbag also includes a forward chamber extending from the main chamber and configured to restrain at least a portion of the vehicle occupant when the airbag is deployed. The forward chamber at least partially overlaps at least one of the inboard and outboard panels of the main chamber when the airbag is stowed.