Shapiro v. McManus, 577 U.S. ___ (2015), was a case in which the Supreme Court of the United States clarified when United States District Court judges must refer cases to three-judge panels.

In a unanimous opinion written by Justice Antonin Scalia, the Court ruled that federal district courts are required to refer cases to a three-judge panel when plaintiffs challenge the constitutionality of the apportionment of congressional districts.

[1] The case results from citizens in Maryland that had challenged the state's redistricting based on the 2010 Census created by Democratic leaders in the state, leading to Republican voters in the 6th district to find their votes diluted and causing ten-term U.S. Representative Roscoe Bartlett to lose in the 2012 election.

The plaintiffs charged that their rights of equal representation and protection under the Article One, Section Two of the U.S. Constitution and freedom of association of the First Amendment had been violated.

At the United States District Court for the District of Maryland, the judge denied the request for a full three-judge hearing, considering that the plaintiff's claims were insubstantial; the decision was summarily affirmed in the Fourth Circuit Appeals Court.