Surgeon General Shiro Ishii (?? ??, Ishii Shiro, [i?i? ?i?o?]; June 25, 1892 – October 9, 1959) was a Japanese microbiologist and army medical officer who served as the director of Unit 731, a biological warfare unit of the Imperial Japanese Army.
Ishii led the development and application of biological weapons at Unit 731 in Manchukuo during the Second Sino-Japanese War from 1937 to 1945, including the bubonic plague attacks on the Chinese cities of Changde and Ningbo, and the planned attack against the United States in the Operation Cherry Blossoms at Night.
Ishii and Unit 731 engaged in forced human experimentation on civilians and prisoners of war that resulted in the death of over 10,000 people, and were responsible for some of the most notorious war crimes of Imperial Japan.
Ishii and Unit 731 were granted immunity in the International Military Tribunal for the Far East by the United States in exchange for information and research for the U.S.