Abstract: A ski boot composed of a rigid sole (1), on the front of which a shell in the form of a shoe (2) is articulated, and of an upper composed of a front part (4) fixed to the shell and of a rear part (6) articulated at the rear of the sole. The rear part (6) is connected to the shell by means of two pivots (15, 16), each interacting with a slot comprising at least two segments (17a and 17b). The first segment (17a) is in the form of an arc of a circle centered approximately on the axis of articulation (7) of the rear part of the upper. The boot closes automatically as a result of the pressure of the foot and likewise opens automatically and widely during the forward bending of the leg accompanied by the lifting of the heel.