Koji Tsuruoka (鶴岡 公二, Tsuruoka Koji, born 10 August 1952) is a Japanese diplomat.

He served as the Japanese ambassador to the United Kingdom from June 2016 until December 2020.

[2] His father was a Japanese diplomat who served as Ambassador to the United Nations.

He joined the Japanese Ministry of Foreign Affairs in 1976.

[4] He then worked in the International Legal Affairs Bureau until 2010.