Abstract: A tourniquet including a belt and buckle with the buckle being formed of st and second buckle parts with a first end belt being connected to the first buckle part formed in a loop, and a second end thereof being releasably clamped between the first and second buckle parts; a pair of pivot pins of the first buckle part being received in recesses of the second buckle part for assembling these parts and maintaining the same in pivotal relationship to each other, and a cam operative upon relative sliding motion between the first and second buckle parts to automatically pivot the buckle parts to clamp the second belt in therebetween. In another embodiment the clamping effect is created by utilizing the elastic force of the belt which acts against a projecting portion of the first buckle belt to pivot the same to its clamping position.