Marquess Kōichi Kido was a Japanese statesman who served as Lord Keeper of the Privy Seal of Japan from 1940 to 1945, and was the closest advisor to Emperor Hirohito throughout World War II. He was convicted of war crimes and sentenced to life imprisonment, of which he served 6 years before being released in 1953.

The Lord Keeper of the Privy Seal of Japan was an administrative post not of Cabinet rank in the government of the Empire of Japan, responsible for being a direct, personal advisor to the emperor, and keeping the Privy Seal of Japan and State Seal of Japan among other things.