The ATP World Tour Masters 1000 is a series of nine tennis tournaments that are part of the Association of Tennis Professionals (ATP) tour, held annually throughout the year in Europe, North America and (as of 2009) Asia. The tournaments are important for the top male players on the professional circuit as the series constitutes the most prestigious tournaments in men's tennis after the four Grand Slam events and the ATP World Tour Finals.

The series was introduced in 1990 with the inception of the ATP Tour by bringing together the nine most prestigious tournaments of the Grand Prix Tour Championship Series (1970–1989). The events were originally known as "Championship Series, Single Week". From 1993 through 1999, the series was known as the Mercedes-Benz Super 9. In 2000, the name was changed to the Tennis Masters Series (TMS) and then changed to ATP Masters Series in 2004. The present name took effect in 2009.

Results in ATP Masters 1000 events earn players more world ranking points than regular tournaments, though not as many as Grand Slam events or the year-end ATP World Tour Finals. Up until 2007, most Masters Series finals were contested as best of five set matches. Currently, all Masters Series events are decided in best of three set matches. Rafael Nadal holds the record for the most titles with 21 (since 1990).

Roger Federer (German pronunciation: [ˈfeːdəʁɐ]) (born 8 August 1981) is a Swiss professional tennis player who held the ATP No. 1 position for a record 237 consecutive weeks from 2 February 2004 to 18 August 2008. Federer has occupied the #1 ranking for 285 overall weeks, one week short of the record 286 weeks held by Pete Sampras. As of 28 May 2012, he is ranked World No. 3. Federer has won a men's record 16 Grand Slam singles titles. He is one of seven male players to capture the career Grand Slam and one of three (with Andre Agassi and Rafael Nadal) to do so on three different surfaces (clay, grass, and hard courts). He is the only male player in tennis history to have reached the title match of each Grand Slam tournament at least five times and also the final at each of the nine ATP Masters 1000 Tournaments. Many sports analysts, tennis critics, and former and current players consider Federer to be the greatest tennis player of all time.

Federer has appeared in an unprecedented 23 career Grand Slam tournament finals, including a men's record ten in a row, and appeared in 18 of 19 finals from the 2005 Wimbledon Championships through the 2010 Australian Open, the lone exception being the 2008 Australian Open. He holds the record of reaching the semifinals or better of 23 consecutive Grand Slam tournaments over five and a half years, from the 2004 Wimbledon Championships through the 2010 Australian Open. At the 2012 Australian Open, he reached a record 31st consecutive Grand Slam quarterfinal. During the course of his run at the 2012 French Open in Roland Garros, Federer eclipsed Jimmy Connors long standing record of 233 match wins in Grand Slam tournaments when he defeated Adrian Ungur in a second round match.