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 and the ATP World Tour Finals. 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.