There is disclosed an offshore vessel mooring and riser inboarding system (12) for a vessel (10) such as an FPSO or FSO. In one embodiment, the system comprises a first mooring element (16) adapted to be located in an offshore environment (18); a riser (20) adapted to be coupled to the first mooring element; a connector assembly (22) 11 adapted to be mounted on the vessel, the connector assembly comprising a second mooring element (28); and a transfer line (32) adapted to be coupled to the riser; wherein the first and second mooring elements are adapted to be connected to facilitate coupling of the riser and the transfer line; and wherein the connector assembly is adapted to permit relative rotation between the vessel and the first mooring element about three mutually perpendicular axes of rotation. This facilitates weathervaning of the vessel relative to the first mooring element, as well as pitch, roll, heave and surge, under applied wind, wave and/or tidal forces.