Koki Saga (嵯峨 宏紀, Saga Kōki, born 25 April 1983)^[1] is a Japanese racing driver.

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The son of Koei Saga, a senior official at Toyota Gazoo Racing,^[2] Saga began kart racing in 1999. In his early career, Saga raced single seaters, such as Formula Toyota and the Japanese Formula 3 Championship. He competed in the Macau Grand Prix in 2008 and 2009 and has competed in Super Taikyu.^[1] He competed in Super Formula for four years with no success.

Saga began competing in Super GT in 2006; due to his ties to Toyota, he has only driven Toyota or Lexus vehicles in his Super GT career. Saga first competed with Toyota Team Cerumo, contributing to the team's first pole position and victory; he was then called up as a third driver for Lexus Team SARD for the Suzuka 1000 km. Saga has been with apr since 2010.

Since the 2018 Super GT Series, Saga has been noted for his antics in pre-race driver introduction segments, consisting of elaborate comedic skits involving costumes, the team's race queens and sometimes other drivers, often performed in a deadpan style.^[3][4]