Seat with folding back-rest equipped with head rests

This motor vehicle seat comprises a cushion (2), a backrest (3), and right and left articulations (5) each connecting a lower lateral part (31) of the backrest (3) to a rear lateral part (21) of the cushion (2). It further comprises right and left linkages each extending between the floor and the corresponding right or left articulation zone, the linkages adopting at least a first configuration, in which the cushion is adjacent to the floor (10) while the backrest is upright, and a second configuration in which the cushion is separated from the floor by a clearance space (7), while the backrest is folded down onto the cushion (2) in a substantially horizontal position.