A tennis court is the venue where the sport of tennis is played. It is a firm rectangular surface with a low net stretched across the centre. The same surface can be used to play both doubles and singles matches. A variety of surfaces can be used to create a tennis court, each with its own characteristics which affect the playing style of the game.

The dimensions of a tennis court are defined and regulated by the International Tennis Federation (ITF) governing body and are written down in the annual 'Rules of Tennis' document. The court is 78 ft (23.77 m) long. Its width is 27 ft (8.23 m) for singles matches and 36 ft (10.97 m) for doubles matches. The service line is 21 ft (6.40 m) from the net. Additional clear space around the court is needed in order for players to reach overrun balls for a total of 60 ft (18 m) wide and 120 ft (37 m) long. A net is stretched across the full width of the court, parallel with the baselines, dividing it into two equal ends. The net is 3 ft 6 in (1.07 m) high at the posts, and 3 ft (0.914 m) high in the center. The net posts are 3 ft (0.914 m) outside the doubles court on each side or, for a singles net, 3 ft (0.914 m) outside the singles court on each side.

Based on the standard rules of tennis, the size of the court is measured to the outside of the respective baselines and sidelines. The "service" lines ("T" and the "service" line) are centered. The ball must completely miss the line to be considered "out". This also means that the width of the line (except for the center service line) is irrelevant to play. The center service line is 2 in (5 cm), the other lines are between 1 and 2 in (3 and 5 cm) wide, whereas the baseline may be up to 4 in (10 cm) wide.

The ITF's Play and Stay campaign promotes playing on smaller courts with slower red, orange, and green balls for younger children. This gives children more time and control so they can serve, rally, and score from the first lesson on courts that are sized to fit their bodies. The ITF has mandated that official competition for children aged 10 years and under should be played on "Orange" courts 18 m (59 ft) long by 6.4 m (21 ft) wide. Competition for children under 8 years is played on "Red" courts that are 11 m (36 ft) long and 5.5 m (18 ft) wide. The net is always 0.8 m high in the center.

Tennis is played on a variety of surfaces and each surface has its own characteristics which affect the playing style of the game. There are four main types of courts depending on the materials used for the court surface: clay courts, hard courts, grass courts and carpet courts. The International Tennis Federation (ITF) lists different surfaces and properties and classifies surfaces into one of five pace settings:

Of the current four Grand Slam tournaments, the Australian and US Open use hard courts, the French Open is played on clay, and Wimbledon, the only Grand Slam to have always been played on the same surface, is played on grass. The Australian Open switched from grass to hard courts in 1988 and in its early years the French championship alternated between clay and sand/rubble courts. The US Open is the only major to have been played on three surfaces; it was played on grass from its inception until 1974, green clay from 1975 until 1977 and hard courts since it moved from the West Side Tennis Club to the National Tennis Center in 1978.

ITF uses the following classification for tennis court surface types:

Clay courts are made of crushed shale, stone or brick. The French Open is the only Grand Slam tournament still played on clay; the courts there are made from crushed red brick (known commonly as "European clay", or terre battue in France).