A surgical instrument comprising: (a) a shaft assembly; (b) an end effector operatively coupled with the shaft assembly, wherein the end effector comprises: (i) a first jaw including an anvil, and (ii) a second jaw configured to removably receive an unspent staple cartridge, wherein at least one of the first or second jaws is configured to pivot relative to the other of the first or second jaws; (c) a firing system extending through at least a portion of the shaft assembly and the end effector, wherein the firing system is operable to staple and cut tissue; and (d) a firing lockout assembly selectively coupled with the firing system, wherein the firing lockout assembly is disposed proximal to the end effector, wherein the firing lockout assembly is configured to: (i) provide the firing system in an unlocked configuration to thereby allow actuation of the firing system in response to the unspent staple cartridge being coupled with the second jaw, and (ii) provide the firing system in a locked configuration to thereby inhibit actuation of the firing system in response to the unspent staple cartridge being absent from the second jaw; wherein the firing lockout assembly includes a lockout member configured to translate from a first position to a second position in response to the unspent staple cartridge being received by the second jaw and a biasing element disposed proximal to the end effector and configured to bias the lockout member toward the locked configuration; the firing system includes an elongate rod that extends along a longitudinal axis, wherein the lockout member includes a deflectable portion (330, 331) disposed proximal to the end effector and configured to deflect along a lateral axis to inhibit actuation of the firing system in the locked configuration, the lateral axis extending transversely to the longitudinal axis; the shaft assembly includes a deflecting member disposed proximal to the end effector, wherein the lockout member is configured to move relative to the deflecting member as the lockout member moves from the locked configuration to the unlocked configuration; characterised in that the deflecting member includes a contact surface (362, 364), wherein the lockout member includes a projection (332, 334) defining a contact surface (336, 338), wherein the biasing element is resiliently biased to a compressed state between the contact surfaces of the deflecting member and the lockout member in the unlocked configuration. (a) a shaft assembly; (b) an end effector operatively coupled with the shaft assembly, wherein the end effector comprises: (i) a first jaw including an anvil, and (ii) a second jaw configured to removably receive an unspent staple cartridge, wherein at least one of the first or second jaws is configured to pivot relative to the other of the first or second jaws; (i) a first jaw including an anvil, and (ii) a second jaw configured to removably receive an unspent staple cartridge, wherein at least one of the first or second jaws is configured to pivot relative to the other of the first or second jaws; (c) a firing system extending through at least a portion of the shaft assembly and the end effector, wherein the firing system is operable to staple and cut tissue; and (d) a firing lockout assembly selectively coupled with the firing system, wherein the firing lockout assembly is disposed proximal to the end effector, wherein the firing lockout assembly is configured to: (i) provide the firing system in an unlocked configuration to thereby allow actuation of the firing system in response to the unspent staple cartridge being coupled with the second jaw, and (ii) provide the firing system in a locked configuration to thereby inhibit actuation of the firing system in response to the unspent staple cartridge being absent from the second jaw; (i) provide the firing system in an unlocked configuration to thereby allow actuation of the firing system in response to the unspent staple cartridge being coupled with the second jaw, and (ii) provide the firing system in a locked configuration to thereby inhibit actuation of the firing system in response to the unspent staple cartridge being absent from the second jaw; wherein the firing lockout assembly includes a lockout member configured to translate from a first position to a second position in response to the unspent staple cartridge being received by the second jaw and a biasing element disposed proximal to the end effector and configured to bias the lockout member toward the locked configuration; the firing system includes an elongate rod that extends along a longitudinal axis, wherein the lockout member includes a deflectable portion (330, 331) disposed proximal to the end effector and configured to deflect along a lateral axis to inhibit actuation of the firing system in the locked configuration, the lateral axis extending transversely to the longitudinal axis; the shaft assembly includes a deflecting member disposed proximal to the end effector, wherein the lockout member is configured to move relative to the deflecting member as the lockout member moves from the locked configuration to the unlocked configuration; characterised in that the deflecting member includes a contact surface (362, 364), wherein the lockout member includes a projection (332, 334) defining a contact surface (336, 338), wherein the biasing element is resiliently biased to a compressed state between the contact surfaces of the deflecting member and the lockout member in the unlocked configuration.