The riser tensioning system (10) includes a tensioning ring (18) for secured engagement with the riser and plurality of hydraulic cylinders (12) extending between the tensioning ring and a floating platform. A gimbal mechanism (42) acts between the platform and the riser to allow the riser axis to tilt relative to the floating platform. One or more elongate torque transfer members (38) extend between the tensioning ring and the gimbal mechanism and allow axial movement of the tensioning ring and the riser with respect to the floating platform.