Abstract: An occupant protection system is provided having a preferable cushion characteristic even at the front part of the seat. In one form, the occupant protection system includes an airbag disposed on S-springs and inflatable to push a seat cushion upward while being supported from below by the S-springs, and a gas generator for inflating the airbag. The airbag extends along the lateral width of the seat, of which the left and right ends are fixed to left and right side frames with bolts, respectively. The airbag is normally disposed on the S-springs in an uninflated state and in a slightly loose state lengthwise. As the seat cushion and the S-springs which support it are moved downward as an occupant sits in the seat cushion, also the airbag can be moved (deformed).