A surgical stapling apparatus. Various embodiments include a handle assembly that has a movable handle that is movable through actuation strokes relative to a stationary handle housing. An actuation is shaft supported at least in part within the stationary handle housing and is movable in response to manipulation of the movable handle. Various embodiments further include a firing lock out assembly that is configured to selectively prevent longitudinal movement of the actuation shaft in a distal direction. A firing release trigger is supported on the movable handle for travel therewith and is configured to interface with the firing lockout assembly to selectively release the firing lockout assembly to permit the actuation shaft to move longitudinally in the distal direction upon manipulation of the movable handle.