Kosuke Kitajima has won back-to-back Olympic titles in both the and m breaststroke. In Beijing, he became the first repeat breaststroke winner in 76 years, succeeding his compatriot Yoshiyuki Tsuruta. Kitajima has had a long rivalry with his American opponent Brendan Hansen, whom he beat at both the and Olympics, as well as at the World Championships (2 times). Hansen in turn beat the Japanese swimmer at the World Championships, and both took one title in Since their rise to the top in , the two have also been fighting for the World Record in both breaststroke events, with Kitajima obtaining both in Kitajima, who in became the first Japanese World Champion in swimming, made the news prior to the Beijing Olympics when he denied wearing swimsuits from his sponsor, Mizuno, instead favoring the supposedly faster Speedo suits.
| Games | Discipline (Sport) / Event | NOC / Team | Pos | Medal | As |
|---|---|---|---|---|---|
| Summer Olympics | Swimming (Aquatics) | JPN | Kosuke Kitajima | ||
| metres Breaststroke, Men(Olympic) | 4 | ||||
| metres Breaststroke, Men(Olympic) | 17 | ||||
| Summer Olympics | Swimming (Aquatics) | JPN | Kosuke Kitajima | ||
| metres Breaststroke, Men(Olympic) | 1 | Gold | |||
| metres Breaststroke, Men(Olympic) | 1 | Gold | |||
| 4 × metres Medley Relay, Men(Olympic) | Japan | 3 | Bronze | ||
| Summer Olympics | Swimming (Aquatics) | JPN | Kosuke Kitajima | ||
| metres Breaststroke, Men(Olympic) | 1 | Gold | |||
| metres Breaststroke, Men(Olympic) | 1 | Gold | |||
| 4 × metres Medley Relay, Men(Olympic) | Japan | 3 | Bronze | ||
| Summer Olympics | Swimming (Aquatics) | JPN | Kosuke Kitajima | ||
| metres Breaststroke, Men(Olympic) | 5 | ||||
| metres Breaststroke, Men(Olympic) | 4 | ||||
| 4 × metres Medley Relay, Men(Olympic) | Japan | 2 | Silver |