Ilie Theodoriu Năstase (born 19 July 1946) is a former World No. 1 Romanian tennis player.

He was ranked world No. 1 in singles from 23 August 1973 to 2 June 1974, and was the first man to hold the top position on the computerized ATP rankings. Năstase is one of the 10 players in history who have won over 100 total ATP titles, with 64 in singles and 45 in doubles.