Ultimate frisbee (officially simply called ultimate) is a non-contact team sport played with a disc flung by hand. Ultimate was developed in 1968 by Joel Silver, Buzzy Hellring, and Jonny Hines in Maplewood, New Jersey. Although ultimate resembles many traditional sports in its athletic requirements, it is unlike most sports due to its focus on self-officiating, even at the highest levels of competition. The term "frisbee" is a registered trademark of the Wham-O toy company, and thus the sport is not formally called "ultimate frisbee", though this name is still in common casual use (and the trademark was licensed to the Ultimate Frisbee Association in 2024). Points are scored by passing the disc to a teammate in the opposing end zone. Other basic rules are that players must not take steps while holding the disc, while interceptions, incomplete passes, and passes out of bounds are turnovers (change in possession). Rain, wind, or occasionally other adversities can make for a testing match with rapid turnovers, heightening the pressure of play.

From its beginnings in the American counterculture of the late 1960s, ultimate has resisted empowering any referee with rule enforcement. Instead, it relies on the sportsmanship of players and invokes the "spirit of the game" to maintain fair play. Players call their own fouls, and dispute a foul only when they genuinely believe it did not occur. Playing without referees is the norm for league play but has been supplanted in club competition by the use of "observers" or "game advisors" to help in disputes, and the professional league employs empowered referees.

In 2012, there were 5.1 million ultimate players in the United States. Ultimate is played across the world in pickup games and by recreational, school, club, professional, and national teams at various age levels and with open, women's, and mixed divisions.

The USA has historically won most of the world titles, though not all. American teams won all three divisions (women's, men's, and mixed gender) at the world championship in 2024, and won the World Games in 2022. Other historically strong nations include Canada, Japan, Australia, and many European countries.

I just remember one time running for a pass and leaping up in the air and just feeling the Frisbee making it into my hand and feeling the perfect synchrony and the joy of the moment, and as I landed I said to myself, 'This is the ultimate game. This is the ultimate game.'

— Jared Kass, one of the inventors of ultimate, interviewed in 2003, speaking of the summer of 1968

Team flying disc games using pie tins and cake pan lids were part of Amherst College student culture for decades before plastic discs were available. As of 2023, the college currently boasts a woman's team called Sparkle Motion (inspired by the dance team in Donnie Darko) and an open team titled Army of Darkness. A similar two-hand, touch-football-based game was played at Kenyon College in Ohio starting in 1942.

From 1965 or 1966 Jared Kass and fellow Amherst students Bob Fein, Richard Jacobson, Robert Marblestone, Steve Ward, Fred Hoxie, Gordon Murray, and others evolved a team frisbee game based on concepts from American football, basketball, and soccer. This game had some of the basics of modern ultimate, including scoring by passing over a goal line, advancing the disc by passing, no travelling with the disc, and turnovers on interceptions or incomplete passes. Kass, an instructor and dorm advisor, taught this game to high school student Joel Silver during the summer of 1967 or 1968 at Northfield Mount Hermon School summer camp.