Ryan Lochte is Michael Phelps' longest-running rival. Ryan had defeated Phelps at London Olympics.
Athletic greats, Usain Bolt and Justin Gatlin were each other's biggest rivals on the field.
During the 1980's English sporting excellence Sebastian Coe and Steve Ovett were rivals in the 1500m and 800m races.
Ben Johnson and Carls Lewis were arch-rivals in the track and field sport during the 1980s.
Yang Chuan-Kwang and Rafer Johnson were rivals in the 1500m race during the 1960's.