Reynolds v. Sims, 377 U.S. 533 (1964), was a landmark United States Supreme Court case in which the Court ruled that the electoral districts of state legislative chambers must be roughly equal in population. Along with Baker v. Carr (1962) and Wesberry v. Sanders (1964), it was part of a series of Warren Court cases that applied the principle of "one person, one vote" to U.S. legislative bodies.