The ATP World Tour is the global elite professional tennis circuit organized by the Association of Tennis Professionals (ATP) and comprises four Grand Slam tournaments (supervised by the International Tennis Federation), the ATP World Tour Masters 1000, the ATP World Tour 500 series, the ATP World Tour 250 series, the ATP World Tour Finals and the Davis Cup (also organized by the International Tennis Federation).
The categories of tennis tournaments organized by the Association of Tennis Professionals are:
ATP World Tour Finals
The ATP World Tour Finals (previously also known as the Tennis Masters Cup) are the season-ending championships of the ATP World Tour, featuring the top eight singles players and doubles teams of the rankings. Winners are awarded up to 1500 rankings points (only or undefeated champions). Unlike most of the other tennis tournaments, the ATP World Tour Finals is not a knock-out tournament as the eight players are divided into two groups of four players and play three round-robin matches against the other three players in their group. The two players with the best records in each group progress to the semifinals, with the winners meeting in the final. The tournament with a rotating locale, is currently held in November on indoors hard court at the O2 Arena in London.
A similar event on the women's tour is the WTA Tour Championships currently held in Istanbul. The most successful player in the history of this tournament is Martina Navratilova with 8 crowns in 12 appearances.
ATP World Tour Masters 1000
The ATP World Tour Masters 1000 is a series of nine tennis tournaments held annually throughout the year in nine cities in Europe, North America and Asia. The series, formerly known as Super 9 or Tennis Masters Series, constitutes the most prestigious tournaments in men's tennis after the four Grand Slam events and the ATP World Tour Finals. Up until 2007, most Masters Series finals were contested as best-of-five sets matches, now all matches are decided in best-of-three sets. All Masters 1000 events except Monte Carlo are mandatory for leading players.
The most successful player of this series who holds the record for the most titles is Rafael Nadal with 21 titles. Roger Federer is on the second place with 20 crowns. The nine Masters 1000 events are:
- Indian Wells (played on hard courts in March)
- Miami (played on hard courts in March/April)
- Monte Carlo (played on clay courts in April)
- Madrid (played on clay courts in May)
- Rome (played on clay courts in May)
- Montreal / Toronto (played on hard courts in August)
- Cincinnati (played on hard courts in August)
- Shanghai (played on hard courts in October)
- Paris (played on indoors hard courts in October/November)
ATP World Tour 500
The ATP World Tour 500 series (previously known as ATP International Series Gold or ATP Championship Series) is the third highest tier of men's tennis tournaments that currently includes 11 tennis tournaments (Rotterdam, Memphis, Acapulco, Dubai, Barcelona, Hamburg, Washington, Beijing, Tokyo, Basel and Valencia), with a number of 500 rankings points to win for the events' singles champions. Tournaments have various draws size of 32, 48 or 56 players for singles competitions. It is mandatory for leading players to enter at least four 500 events, including at least one after the US Open.
ATP World Tour 250
The ATP World Tour 250 series is the lowest tier of men's tennis tournaments and includes 40 tournaments, with a number of 250 rankings points to win for the events' singles champions. The tournaments mostly have a draw size of 28 or 32 players for singles competitions.