Kenji Watanabe (渡辺 健司, Watanabe Kenji, July 17, 1969 – September 18, 2017) was a Japanese breaststroke swimmer. He represented his native country in three consecutive Summer Olympics, starting in 1984. His best Olympic result was the 7th place (2:14.70) in the Men's 200m Breaststroke event at the 1992 Summer Olympics in Barcelona, Spain. He was the grandson of Hisakichi Toyoda, who won a gold medal in the 4 × 200 m freestyle in the 1932 Summer Olympics. At the 1986 Asian Games in Seoul, Watanabe won the gold medal in the 200m breaststroke and the bronze medal in the 100m breaststroke.