Abstract: A ski boot comprising an adjustable support for the foot positioned in the heel portion, the support being a substantially U-shaped spring (4) whose crosspiece (5) is positioned in the heel portion of the shell (7) of the boot and whose legs (6) extend forward on both sides inside the shell (7), embracing the foot substantially between the ankle and the heel-bone, the legs (6) being adjustable in various relative positions with respect to each other by an adjusting means (9; 18; 21; 24; 26; 29; 32; 33; 37 38) engaging the cross piece (5) or the legs (6).