Abstract: Described is a fastening device for jewellery comprising a first element and a second element which can be fixed to respective ends of jewellery, wherein the first element has a top surface and a bottom surface, in which a socket is formed; the second element has a top surface, a bottom surface and a head, configured to interlock in a complementary way with the socket, so as to reversibly couple the first element with the second element; the second element comprises a groove, formed on its top surface, in which a sliding slider is housed, the first element comprises a recess, in a position adjacent to the socket, delimited by its top surface, so that, when the head is inserted in the socket, the slider remains in contact with the top surface of the first element at the recess, preventing the head from disengaging the socket and the second element from separating from the first element.