John Henry Kagi, also spelled John Henri Kagi (March 15, 1835 – October 17, 1859), was an American attorney, abolitionist, and second in command to John Brown in Brown's failed raid on Harper's Ferry. He bore the title of "Secretary of War" in Brown's "provisional government." At age 24, Kagi was killed during the raid. He had previously been active in fighting on the abolitionist side in 1856 in "Bleeding Kansas". He was an excellent debater and speaker.