Clasp for a bracelet of the type comprising first and second free ends, the clasp comprising: first and second bracelet fastening members (172, 174) intended to be made respectively integral with said first and second free ends of the bracelet, said fastening members (172, 174) being movable in relation to one another between at least one open position and a closed wearing position, in which said members are closer to one another than in the open position, to close the bracelet and define a useful length therefore; at least one locking member (210, 217) arranged to hold said bracelet fastening members (172, 174) in the closed position thereof, at least one control member for said locking member (210, 217) arranged to unlock the clasp in response to an action of a user and to change from said closed position to said open position; a device for adjusting the useful length of the bracelet comprising: an adjusting member (184, 186, 226, 228) carrying said first bracelet fastening member, and at least one lock capable of having a default closed state, in which said adjusting member (184, 186, 226, 228) is fixed, and an open state, in which said adjusting member (184, 186, 226, 228) is free to slide in the direction of the length of the bracelet with respect to said second bracelet fastening member to modify the useful length of the bracelet, characterised in that said adjusting device is distinct from said locking member (210, 217), and said lock is arranged to change from the closed state to the open state thereof by action of the user on said control member of the locking member (210, 217) such that said adjusting member (184, 186, 226, 228) is capable of being shifted independently of the open or closed state of the clasp, said control member comprises a push-piece capable of being displaced in a substantially perpendicular direction to the longitudinal direction of the bracelet in response to an action of the user, said push-piece being independent of said lock. first and second bracelet fastening members (172, 174) intended to be made respectively integral with said first and second free ends of the bracelet, said fastening members (172, 174) being movable in relation to one another between at least one open position and a closed wearing position, in which said members are closer to one another than in the open position, to close the bracelet and define a useful length therefore; at least one locking member (210, 217) arranged to hold said bracelet fastening members (172, 174) in the closed position thereof, at least one control member for said locking member (210, 217) arranged to unlock the clasp in response to an action of a user and to change from said closed position to said open position; a device for adjusting the useful length of the bracelet comprising: an adjusting member (184, 186, 226, 228) carrying said first bracelet fastening member, and at least one lock capable of having a default closed state, in which said adjusting member (184, 186, 226, 228) is fixed, and an open state, in which said adjusting member (184, 186, 226, 228) is free to slide in the direction of the length of the bracelet with respect to said second bracelet fastening member to modify the useful length of the bracelet, an adjusting member (184, 186, 226, 228) carrying said first bracelet fastening member, and at least one lock capable of having a default closed state, in which said adjusting member (184, 186, 226, 228) is fixed, and an open state, in which said adjusting member (184, 186, 226, 228) is free to slide in the direction of the length of the bracelet with respect to said second bracelet fastening member to modify the useful length of the bracelet, characterised in that said adjusting device is distinct from said locking member (210, 217), and said lock is arranged to change from the closed state to the open state thereof by action of the user on said control member of the locking member (210, 217) such that said adjusting member (184, 186, 226, 228) is capable of being shifted independently of the open or closed state of the clasp, said control member comprises a push-piece capable of being displaced in a substantially perpendicular direction to the longitudinal direction of the bracelet in response to an action of the user, said push-piece being independent of said lock.