A surgical instrument that comprises a housing, an elongate shaft configured for operable attachment to a surgical end effector, and a selectively lockable rotation system is disclosed. The selectively lockable rotation system comprises a mounting member coupled to the elongate shaft and being rotatably supported on the housing for selective rotation relative to the housing about a longitudinal axis defined by the elongate shaft. The selectively lockable rotation system further comprises a switch member supported for selective longitudinal movement relative to the housing and the mounting member between an unlocked position wherein the mounting member is freely rotatable relative to the housing and a locked position wherein a locking formation on a distal end of the switch member is in retaining engagement with the mounting member to prevent the mounting member and the elongate shaft from rotating relative to the housing.