In U.S. Supreme Court history, "The switch in time that saved nine" is the phrase—originally a quip by humorist Cal Tinney—about what was perceived in 1937 as the sudden jurisprudential shift by associate justice Owen Roberts in the 1937 case West Coast Hotel Co. v. Parrish. Conventional historical accounts portrayed the Court's majority opinion as a strategic political move to protect the Court's integrity and independence from President Franklin Roosevelt's court-reform bill (also known as the "court-packing plan"), but later historical evidence gives weight to Roberts' decision being made much earlier, before the bill's introduction.

The term itself is a reference to the aphorism "a stitch in time saves nine", meaning that preventive maintenance before something breaks is less work than fixing that thing after it breaks.