The Supreme Court has recently insisted that plaintiffs must have standing for every claim that they raise. But this claim-specific approach to standing is at odds with established practice in several contexts, including rulings on the severability of statutes. Courts often permit plaintiffs to claim that statutory provisions should be invalidated pursuant to severability doctrine, without requiring that they have standing for those claims. This Article argues that existing practice for severability is a form of “supplemental standing.” Supplemental standing is analogous to supplemental jurisdiction. It allows a plaintiff with standing for one claim to raise related claims, even if the plaintiff lacks standing for those other claims. Although the Supreme Court has purported to reject this concept, current law effectively grants supplemental standing for severability claims—and with good reason. When a court rules that part of a statute is unconstitutional, a ruling on severability is necessary to give effect to Congress’s intent regarding the remainder of the statute. Supplemental standing permits those rulings, but claim-specific standing would often prevent them. In the severability context, therefore, supplemental standing is more faithful to the central purpose of standing doctrine: preserving the separation of powers. This Article contends that current practice also implicitly grants supplemental standing in additional contexts, including facial challenges to statutes and cases involving multiple plaintiffs. These examples suggest that, while the claim-specific approach to standing is a useful default rule, the Court has been wrong to insist on that approach as a categorical matter. The Article concludes by exploring additional circumstances in which shifting to a supplemental- standing approach appears to be justified on separation of powers grounds.