Abstract: The invention refers to a ski boot made from synthetic plastic material, with separate boot and leg portions.The ski boot according to the invention presents a leg portion separable from the boot, comprising a part higher than the ankles and a lower part rigidly bound to the sole. The two parts of the leg portion may be built in a single piece or separately. In the latter case, the two parts are articulated to each other in the ankle region by means of pivotal pins.The ski boot according to the invention overcomes the drawback presented by the previously known ski boots, wherein the boot's articulation area dilates as a consequence of the fore rocking of the leg portion, and thus reduces the clamping action of the boot on the skier's foot, just when the skier's leg is expected to transmit the strongest thrust to the ski, through the ski boot.