Abstract: Clasp for a piece of jewellery or wristwatch, including a stretcher like structure with a first housing in which a first push-piece and a second push-piece are moveable on a first bearing surface against an elastic return means, and held by at least one closure plate able to occupy a closure position in a second housing. The clasp includes at least one resilient locking element for this closure plate, including a push-button, held in this stretcher like structure and arranged, in a compressed position, to permit the motion of the closure plate and, in a relaxed position, to immobilise this closure plate in the closure position via the cooperation of this push-button with a fourth housing comprised in the closure plate.