Koki Mitani
- Birthday: 1961-07-08
- Place of birth: Setagaya, Tokyo, Japan
- Also know as: Kōki Mitani
Kōki Mitani (三谷 幸喜, Mitani Kōki; born July 8, 1961) is a Japanese playwright, screenwriter, actor and film director. He studied dramatics at Nihon University. He has been described by The Japan Times as "far and away the nation's best-known dramatist". In 2023, Mitani was the recipient of the 15th annual Juzo Itami Award.
