Daniil Sergeyevich Medvedev is a Russian professional tennis player. He has been ranked as high as world No. 1 in men's singles by the Association of Tennis Professionals (ATP), and is the current world No. 4. Medvedev has won 20 ATP Tour singles titles, including the 2021 US Open and 2020 ATP Finals. Medvedev defeated world No. 1 Novak Djokovic in the final to deny him the Grand Slam. In the latter, he became the only player to defeat the top three ranked players in the world en route to the year-end championship title. He has also won six Masters titles and contested six major finals. His six Masters titles all came in different venues, making him only the sixth player to win Masters titles at six different venues.

The Association of Tennis Professionals (ATP) is the governing body of the men's professional tennis circuits – the ATP Tour, the ATP Challenger Tour and the ATP Champions Tour. It was formed in September 1972 by Donald Dell, Jack Kramer, and Cliff Drysdale to protect the interests of professional tennis players, and Drysdale became the first president. Since 1990 the association has organized the ATP Tour, the worldwide tennis tour for men and linked the title of the tour with the organization's name. It is the governing body of men's professional tennis. In 1990 the organization was called the ATP Tour, which was renamed in 2001 as just ATP and the tour being called ATP Tour. In 2009 the name of the tour was changed again and was known as the ATP World Tour, but changed again to the ATP Tour by 2019. It is an evolution of the tour competitions previously known as Grand Prix tennis tournaments and World Championship Tennis (WCT). The ATP's global headquarters are in London. ATP Americas is based in Ponte Vedra Beach, Florida; ATP Europe is headquartered in Monaco; and ATP International, which covers Africa, Asia and Australasia, is based in Sydney, Australia.