The US Open tennis tournament is one of the oldest tennis championships in the world, first contested in 1881. The tournament is chronologically the fourth and final Grand Slam tennis tournament each year. It is held annually in August and September over a two-week period (the weeks before and after Labor Day weekend). The main tournament consists of five different event championships: men's and women's singles, men's and women's doubles, and mixed doubles, with additional tournaments for senior, junior, and wheelchair players. Since 1978, the tournament has been played on acrylic hard court at the USTA Billie Jean King National Tennis Center at Flushing Meadows-Corona Park in Queens, New York City.

The US Open differs from the other three Grand Slam tournaments in that there are final-set tiebreaks. In the other three majors, the fifth set for the men and the third set for the women continue until someone wins by two games.

The US Open has grown from an exclusive entertainment event for high society to a championship for more than 600 male and female professional players who, as of 2008, compete for total prize money of over US$19 million, with $1.5 million for each winner of the singles tournaments.