A ski boot comprising: a substantially rigid foot-casing which is shaped so as to accommodate the user's foot, and has the lower part structured so as to couple with a ski binding device; a substantially rigid cuff which is shaped so as to surround the lower part of the user's leg, and is pivotally joined to the foot-casing so as to be able to swing about a rotation axis substantially perpendicular to the midplane of the boot; and foot-casing closing means adapted to selectively tighten the foot-casing against the user's foot; the foot-casing being superiorly provided with a main opening from which the user's leg comes out, and with a longitudinal slit that branches off from said main opening and extends along the upper part of the foot-casing, towards the front tip of the same foot-casing; wherein said foot-casing closing means comprise: a plurality of transversal flexible tongues that are arranged inside the foot-casing astride and transversal to a first longer lateral edge of the longitudinal slit, and are firmly fixed to the foot-casing so as to extend cantilevered inside the longitudinal slit towards a second longer lateral edge of the longitudinal slit, opposite to said first longer lateral edge; a series of substantially non-deformable cable-return members that are located on the foot-casing along or close to the second longer lateral edge of the longitudinal slit; and a cable-winding winch which is fixed onto the foot-casing, close to the second longer lateral edge of the longitudinal slit, or onto one of the transversal flexible tongues, and is provided with a tightening cable that exits from the cable-winding winch and engages in pass-through and freely slidable manner both the distal ends of the transversal flexible tongues and the cable-return members. a substantially rigid foot-casing which is shaped so as to accommodate the user's foot, and has the lower part structured so as to couple with a ski binding device; a substantially rigid cuff which is shaped so as to surround the lower part of the user's leg, and is pivotally joined to the foot-casing so as to be able to swing about a rotation axis substantially perpendicular to the midplane of the boot; and foot-casing closing means adapted to selectively tighten the foot-casing against the user's foot; the foot-casing being superiorly provided with a main opening from which the user's leg comes out, and with a longitudinal slit that branches off from said main opening and extends along the upper part of the foot-casing, towards the front tip of the same foot-casing; wherein said foot-casing closing means comprise: a plurality of transversal flexible tongues that are arranged inside the foot-casing astride and transversal to a first longer lateral edge of the longitudinal slit, and are firmly fixed to the foot-casing so as to extend cantilevered inside the longitudinal slit towards a second longer lateral edge of the longitudinal slit, opposite to said first longer lateral edge; a series of substantially non-deformable cable-return members that are located on the foot-casing along or close to the second longer lateral edge of the longitudinal slit; and a cable-winding winch which is fixed onto the foot-casing, close to the second longer lateral edge of the longitudinal slit, or onto one of the transversal flexible tongues, and is provided with a tightening cable that exits from the cable-winding winch and engages in pass-through and freely slidable manner both the distal ends of the transversal flexible tongues and the cable-return members. a plurality of transversal flexible tongues that are arranged inside the foot-casing astride and transversal to a first longer lateral edge of the longitudinal slit, and are firmly fixed to the foot-casing so as to extend cantilevered inside the longitudinal slit towards a second longer lateral edge of the longitudinal slit, opposite to said first longer lateral edge; a series of substantially non-deformable cable-return members that are located on the foot-casing along or close to the second longer lateral edge of the longitudinal slit; and a cable-winding winch which is fixed onto the foot-casing, close to the second longer lateral edge of the longitudinal slit, or onto one of the transversal flexible tongues, and is provided with a tightening cable that exits from the cable-winding winch and engages in pass-through and freely slidable manner both the distal ends of the transversal flexible tongues and the cable-return members.