John Paul Stevens (born April 20, 1920) is the senior Associate Justice of the Supreme Court of the United States. He joined the Supreme Court in 1975 and is the oldest member of the Court. He was appointed to the Court by Republican President Gerald Ford. Although Stevens is widely considered to be on the liberal side of the court, Ford praised Stevens in 2005: "He is serving his nation well, with dignity, intellect and without partisan political concerns." He is also the only current Justice to have served under three Chief Justices (Warren E. Burger, William Rehnquist, and John G. Roberts).

Early in his tenure on the Supreme Court Stevens had a moderate voting record. He voted to reinstate capital punishment in the United States and opposed the racial quota system program at issue in Regents of the University of California v. Bakke. But on the more conservative Rehnquist Court, Stevens tended to side with the more liberal-leaning Justices on issues such as abortion rights, gay rights and federalism. His Segal-Cover score, a measure of the perceived liberalism/conservatism of Court members when they joined the Court, places him squarely in the ideological center of the Court. A 2003 statistical analysis of Supreme Court voting patterns, however, found Stevens the most liberal member of the Court.

Stevens' jurisprudence has usually been characterized as idiosyncratic. Stevens, unlike most justices, usually writes the first drafts of his opinions himself and reviews petitions for certiorari within his chambers instead of having his law clerks participate as part of the cert pool. He is not an originalist (such as fellow Justice Antonin Scalia) nor a pragmatist (such as Judge Richard Posner), nor does he pronounce himself a cautious liberal (such as Justice Ruth Bader Ginsburg). He has been considered part of the liberal bloc of the court since the mid-1980s, though he publicly called himself a judicial conservative in 2007.Stevens was once an impassioned critic of affirmative action, voting in 1978 to invalidate the racial quota system program at issue in Regents of the University of California v. Bakke. He also dissented in 1980's Fullilove v. Klutznick, which upheld a minority set-aside program. He shifted his position over the years and voted to uphold the affirmative action program at the University of Michigan Law School challenged in 2003's Grutter v. Bollinger.