A surgical stapling instrument is disclosed. The stapling instrument comprises an end effector including a staple cartridge comprising a circular array of staple cavities and staples removably stored in the staple cavities and, in addition, an anvil configured to deform the staples which is movable toward the staple cartridge to clamp tissue therebetween. The anvil is movable away from the staple cartridge to release the tissue after the tissue has been stapled. The stapling instrument further comprises a lockout configured to prevent the anvil from being moved toward the staple cartridge once again until the staple cartridge has been replaced with an unfired staple cartridge.
