A surgical instrument comprising: a firing member assembly including a portion supported for selective axial movement in a distal direction and a proximal direction; a drive unit, comprising: a motor including a motor shaft; and a gear assembly drivingly coupled to the motor shaft and including an output shaft assembly configured to apply rotary motions to the firing member assembly such that upon rotation of the motor shaft in a first rotary direction, the portion of the firing member assembly is axially driven in the distal direction and upon rotation of the motor shaft in a second rotary direction, the portion of the firing member assembly is axially driven in the proximal direction and wherein the surgical instrument further comprises: a retraction assembly interfacing with the firing member assembly for manually applying other rotary motions to the firing member assembly in the second rotary direction when the motor is deactivated; and locking means interfacing with the retraction assembly and the drive unit for preventing transfer of the other rotary motions to the motor shaft during operation of the retraction assembly and while the gear assembly remains drivingly coupled to the motor shaft; and wherein the surgical instrument further comprises a housing and wherein the motor includes a motor housing that is non-movably supported within the housing and characterized in that the gear assembly comprises: a gear box housing coupled to the motor housing; a gear train assembly operably supported within the gear box housing in driving engagement with the motor shaft; and a lockable ring gear rotatably supported by the gear box housing and in driving engagement with the gear train assembly and the output shaft assembly and wherein said locking means comprises a movable shift ring assembly being movable from a locked position wherein said shift ring assembly lockingly engages the lockable ring gear to prevent rotation thereof relative to the gear box housing to an unlocked position wherein the lockable ring gear is free to rotate relative to the gear box housing. a firing member assembly including a portion supported for selective axial movement in a distal direction and a proximal direction; a drive unit, comprising: a motor including a motor shaft; and a gear assembly drivingly coupled to the motor shaft and including an output shaft assembly configured to apply rotary motions to the firing member assembly such that upon rotation of the motor shaft in a first rotary direction, the portion of the firing member assembly is axially driven in the distal direction and upon rotation of the motor shaft in a second rotary direction, the portion of the firing member assembly is axially driven in the proximal direction and wherein the surgical instrument further comprises: a motor including a motor shaft; and a gear assembly drivingly coupled to the motor shaft and including an output shaft assembly configured to apply rotary motions to the firing member assembly such that upon rotation of the motor shaft in a first rotary direction, the portion of the firing member assembly is axially driven in the distal direction and upon rotation of the motor shaft in a second rotary direction, the portion of the firing member assembly is axially driven in the proximal direction and wherein the surgical instrument further comprises: a retraction assembly interfacing with the firing member assembly for manually applying other rotary motions to the firing member assembly in the second rotary direction when the motor is deactivated; and locking means interfacing with the retraction assembly and the drive unit for preventing transfer of the other rotary motions to the motor shaft during operation of the retraction assembly and while the gear assembly remains drivingly coupled to the motor shaft; and wherein the surgical instrument further comprises a housing and wherein the motor includes a motor housing that is non-movably supported within the housing and characterized in that the gear assembly comprises: a gear box housing coupled to the motor housing; a gear train assembly operably supported within the gear box housing in driving engagement with the motor shaft; and a lockable ring gear rotatably supported by the gear box housing and in driving engagement with the gear train assembly and the output shaft assembly and wherein said locking means comprises a movable shift ring assembly being movable from a locked position wherein said shift ring assembly lockingly engages the lockable ring gear to prevent rotation thereof relative to the gear box housing to an unlocked position wherein the lockable ring gear is free to rotate relative to the gear box housing. a gear box housing coupled to the motor housing; a gear train assembly operably supported within the gear box housing in driving engagement with the motor shaft; and a lockable ring gear rotatably supported by the gear box housing and in driving engagement with the gear train assembly and the output shaft assembly and wherein said locking means comprises a movable shift ring assembly being movable from a locked position wherein said shift ring assembly lockingly engages the lockable ring gear to prevent rotation thereof relative to the gear box housing to an unlocked position wherein the lockable ring gear is free to rotate relative to the gear box housing.