#10 Rafael Nadal – 22 years, 76 days
After winning his fifth grand slam title at Wimbledon 2008, Rafael Nadal became the World No.1 replacing Roger Federer
#9 Jimmy Connors – 21 years, 330 days
Jimmy Connors became the World No.1 after winning Wimbledon in 1974 and stayed atop for 160 consecutive weeks
#8 Pete Sampras – 21 years, 243 days
After winning the 1993 Miami Open, Pete Sampras became the 11th man in history to become the World No.1 in ATP Rankings.
#7 Jim Courier – 21 years, 177 days
Just a few weeks after winning the 1992 Australian Open, Jim Courier became the World No.1 as he got past Stefan Edberg
#6 Bjorn Borg – 21 years, 78 days
Just a few weeks after winning his fourth major title, Bjorn Borg became the World No.1 in August 1977
#5 Andy Roddick – 21 years, 65 days
Andy Roddick became the World No.1 after he won the 2003 US Open but stayed at the top for only 13 weeks because of Roger Federer's dominance at the same time
#4 John McEnroe – 21 years, 16 days
John McEnroe had a tight World No.1 fight with Bjorn Borg in 1980 and in March 1980, became the World No.1 for the first time
#3 Marat Safin – 20 years, 298 days
After winning the 2000 US Open, Marat Safin became the World No.1 for the first time and during his career, stayed at the top for a total of 9 weeks
#2 Lleyton Hewitt – 20 years, 268 days
After winning the 2001 US Open, Lleyton Hewitt became the youngest World No.1 and stayed so for over two decades. He was the Word No.1 for 80 weeks throughout his career.
#1 Carlos Alcaraz – 19 years, 129 days
Having his breakthrough season, Carlos Alcaraz won the 2022 US Open and as a result, became the youngest World No.1 in tennis history