A connector for connecting the abutted end portions of two pipes (4,5) comprises a ring (1) having a pair of radially inwardly extending surfaces (2,3) directed towards each other and each for engagement with a radially outwardly extending surface (8,9) on a respective pipe end, the surfaces (8,9) on the pipe ends being directed away from the respective pipe ends. The connector includes operating means (12) for causing radial expansion of the ring to disengage the ring from one of the pipes (5), the ring remaining engaged with the other pipe (4). To this end the corresponding surfaces (2,8) on the ring and the pipe (4) have a greater radial extent than the surfaces (3,9) so that these surfaces remain engaged for all conditions of use of the connector. The connector is particularly suited for connecting the pipe sections of a pipe string for use in the drilling and/or completion of offshore oil or gas wells.