A seat for a vehicle, including a seating part pivoting about a pivot connection, a pivot connection allowing the seating part to be lowered into a substantially horizontal position or lifted against a back rest, the lowering of the seating part being limited in the course thereof by at least one first abutment that can release the lowering following an impact, the being characterized in that the seating part includes at least two adjacent panels that can carry out a fold-back movement in relation to each other about an axis parallel to the pivot connection between the seating part and the back rest in such a way as to be able to bring the upper faces of the panels towards each other.