A seat includes a seatback. The seat includes a seat bottom extending away from the seatback in a seat-forward direction to a front of the seat bottom distal to the seatback. The seat bottom has a top surface defining an occupant-leg area. The seat includes an airbag supported by the seat bottom at the front of the seat bottom and inflatable from an uninflated position to an inflated position. The airbag in the inflated position extends away from the seat bottom in the seat-forward direction and includes an uppermost surface positioned below the occupant-leg area of the seat bottom.