It was on 23 August 1973 that the Association of Tennis Professionals (ATP) published the first computerized system of ranking all the singles players in the world. The rankings for doubles, meanwhile, were first released on 1 March 1976.
Ilie Nastase of Romania was the first ATP singles World No. 1, whereas Bob Hewitt of South Africa was the first doubles World No. 1. Prior to 1973, there was no standardized ranking system in place, and players were ranked subjectively by different tennis magazines, journalists and experts.
26 singles players have been ranked World No. 1 in the 35 years since inception of the rankings, with Chilean Marcelo Rios the only player to ascend to the top despite not having won a Grand Slam tournament.
Of the 26 players who have been ranked World No. 1, 17 of them have gone on to finish the year as the top-ranked player. The current World No. 1 is 14-time Grand Slam champion Novak Djokovic.
Here, we look at five players who have held the World No. 1 ranking for the most weeks consecutively:
#5 Pete Sampras
'Pistol' Pete Sampras was one of the greatest grasscourt players of all time, and he ushered in an era dominated by Americans like himself and fellow countrymen Andre Agassi and Jim Courier.
In the 1970s and 1980s, American women like Martina Navratilova and Chris Evert dominated the women's field. In the 1990s, it was the turn of the men to do so.
Sampras was ranked the year-end World No. 1 on six consecutive occasions (1993 to 1998 inclusive) - an all-time record. Between 15 April 1996 to 28 March 1998, Sampras was the number 1 ranked player without any interruption - that is, for a total of 102 consecutive weeks.
During this period, he won four Grand Slam titles. In all, Sampras was the top-ranked player in the world for a total of 286 weeks.