ATP Masters Series

The ATP Masters Series was a series of nine tennis tournaments that formed part of the men's Association of Tennis Professionals (ATP) tour, held annually throughout the year in Europe, North America. The tournaments were important for the top male players on the professional circuit as the series constituted the most prestigious tournaments in men's tennis after the four Grand Slam events. The events were known as the Championship Series, Single Week from 1990 to 1995, the Mercedes-Benz Super 9 from 1996 to 1999, the Tennis Masters Series from 2000 to 2004 and the ATP Masters Series until 2008.

The series was introduced in 1990 with the inception of the ATP Tour by bringing together the nine most prestigious tournaments of the preceding Grand Prix tennis circuit. Results in ATP Masters Series events earned 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, but from 2008 all Masters Series events were decided in best of three set matches.

As part of a shake-up of the tennis circuit in 2009, the Masters Series became the ATP World Tour Masters 1000, with the addition of the number 1000 referring to the number of ranking points earned by the winner of each tournament. Contrary to earlier plans, the number of tournaments has not been reduced from nine to eight and the Monte Carlo Masters remains part of the series although, unlike the other events, it does not have a mandatory player commitment. The Hamburg Masters event was downgraded to an ATP World Tour 500 event. The Madrid Masters moved to May and onto clay courts. A new tournament in Shanghai replaced the Hamburg Masters and took over Madrid's former October indoor slot. In 2011, six of the nine "1000" level tournaments were combined ATP and WTA events.

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