John Isner (American professional tennis player).
- Full Name: John Robert Isner
- Date of Birth: April 26, 1985
- Place of Birth: TGreensboro, North Carolina, U.S.
- Country: United States
- Residence: Dallas, Texas, U.S.
- Height: 6 ft 10 in (2.08 m)
- Turned Pro: 2007
- Plays: Right-handed (two-handed backhand)
- Official website: www.johnisner.com