Abstract: A seat with a reversible back rest having on each side of the cushion (14), two coupling rods (20, 22) articulated on the lower part of the back rest (18) and on a vertical support plate (16) at two points (24, 26) situated on a same horizontal line, with the result that the back rest may pivot between two service positions symmetrical relative to the mid point (x-y) of the segment formed by said two points.