Jack Sock (born September 24, 1992) is an American professional tennis player who is currently ranked world No. 21 in men's singles by the Association of Tennis Professionals (ATP). He is one of the top ranked American men in both singles and doubles on the ATP Tour. A former junior US Open champion, Sock's singles success is highlighted by 7 ATP finals, including three titles. His career best result came at the 2017 Indian Wells Masters, where he reached the semi-finals.