<P> In tennis, the ATP World Tour Masters 1000 is a term applied to a series of nine men's tennis tournaments that are ranked below the four Majors and Year - End Championships and are the most prestigious tournaments on the ATP World Tour . The circuit began in 1970, two years after the Open Era when tennis became professional, and has undergone several name changes and slight alterations to the format, in line with overhauls of the tour by the Association of Tennis Professionals . </P> <P> A number of players hold records for winning the tournaments multiple times, while other records are achieved for successive tournament wins, mini-combination victories amongst others . </P> <P> Ivan Lendl and Novak Djokovic are the only players to win all nine events during their careers . However, since the creation of the "Masters 1000" in 2009, Novak Djokovic is the only player to claim all nine ATP Masters 1000 events . Winning all nine events during a career has been called a "Career' Golden Masters"'. Rafael Nadal has won the most number of ATP Masters 1000 singles titles . He has won 33 titles to date . Bob Bryan and Mike Bryan have won the most doubles titles of all - time with 38 . </P> <P> The circuit began in 1970 with the inception of the Grand Prix Tour Championship Series (1970--1989). However, with the advent of the ATP Tour in 1990 the events became known as the ATP Championship Series, Single Week for six years from 1990 to 1995 . From 1996 through 1999, the series was known as the Mercedes - Benz Super 9 . In 2000, the name was changed to the Tennis Masters Series and then changed to ATP Masters Series in 2004 . The present name, ATP World Tour Masters 1000, took effect in 2009 . </P>

Who has won the most tennis masters titles