The Association of Tennis Professionals (ATP) is the main governing body of the men's tennis circuit - the ATP Tour, but also the lower-tier ATP Challenger Tour, and the circuit for former professionals, the ATP Champions Tour.
It was launched in 1972 by Donald Dell, Jack Kramer, and Cliff Drysdale, and despite a few changes over the years, the ATP has been overlooking the men's professional circuit for over 50 years. The women's circuit's governing body is called the Women's Tennis Association (WTA).
The ATP should protect the player's interests and communicate with tournaments, but after not being happy with how the players were represented, one of the most successful players in history, Novak Djokovic, started the Professional Tennis Players Association (PTPA), which wanted to provide better representation for tennis players.
Currently, the ATP oversees over 60 tournaments in more than 30 countries, with the ATP Tour featuring tournaments divided into multiple categories - ATP Finals, ATP Masters 1000, ATP 500, and ATP 250.
On the ATP Challenger Tour, the ATP oversees over 150 tournaments in more than 40 countries. The four Grand Slam tournaments - Australian Open, Roland Garros, Wimbledon, and US Open, are all overseen by the International Tennis Federation (ITF), which is another governing body in tennis.
The ATP also publishes weekly ATP Rankings into which players amass points earned in all tennis tournaments, regardless of whether they are organized by the ATP or ITF, over a 52-week period.
In the more than 50-year history of the ATP Rankings, which were first introduced on August 23, 1973, Novak Djokovic has been the most successful player, amassing over 400 weeks on the world no. 1 spot.
Players have representation in the ATP's Players Council, and new members are periodically elected. The council includes representatives from multiple continents and ranking levels, as well as players in singles and doubles.
