Paris: Spanish tennis star Rafael Nadal got the better of South Korean Hyeon Chung 7-5, 6-4 to advance into the Paris Masters third round.
With the win here on Wednesday evening, Nadal secures the ATP ranking's top spot until the end of the year for the first time since 2013.
Nadal's top ranking comes after his main rival, Swiss Roger Federer, pulled out of this year's last Masters event, reports Efe news agency.
The 31-year-old Nadal became the oldest player to top the rankings in its 44-year history.
"I'm very, very happy for everything. It has been an amazing year. One year ago, for sure I never dreamed about being World No. 1 again... It's something that means a lot to me. But the season is not over," Nadal said on-court.
Both players exchanged breaks early in the first set, but Nadal managed to carve out a 4-2 lead.
While serving for the set, the 21-year-old Chung, ranked world number 55, broke Nadal's service again, only to make Nadal sweat a little more before the Spaniard clinched the set.
The 16-time Grand Slam champion put pressure on Chung's serve as the second set wore on, earning a break in the ninth game, which proved to be decisive.