Who was the first tennis player to be ranked world No. 1 in the ATP rankings?

Ilie Năstase was the first tennis player ranked world No. 1 in the ATP rankings, reaching the top spot on August 23, 1973.

The Association of Tennis Professionals introduced its computer-based rankings in 1973 to provide a standardized way to measure men’s singles performance. Năstase became the inaugural No. 1 and spent 40 weeks at the top during his career. His ranking reflected a period of outstanding results, including his 1973 French Open singles title.

Năstase was one of the most versatile players of his generation. He won two Grand Slam singles titles, seven major titles across singles and doubles, and four year-end Masters Grand Prix championships. His speed, touch, imagination, and sometimes theatrical behavior made him one of tennis’s most distinctive stars.

A frequent mistake is choosing Rod Laver, who dominated the sport before the ATP computer rankings began. Jimmy Connors and John Newcombe also became No. 1 later, but neither was the inaugural leader. The answer refers specifically to the ATP rankings, not informal newspaper rankings or pre-1973 historical assessments.