William Henry Harrison Hart (January 25, 1846/1848 – December 24, 1918) was the 16th California Attorney General. Prior to this position, he claims to have been a United States Secret Service agent and have fought in the American Civil War.

William Henry Harrison Hart was born on January 25, 1846 (or 1848^[1]), in England.^[2] He immigrated to the United States with his family at age four.^[1] Hart claimed to have been kidnapped by the Blackhawk Indians at the age of eight. He was then orphaned and orphaned at age eleven. Hart struggled through a difficult childhood which led to his desire for danger and his allegedly joining the United States Secret Service at only age 14. Hart also claimed to have fought for the Union during the Civil War.^{[1][clarification needed]}

On November 4, 1890, Hart was elected as California Attorney General and took office on January 5, 1891. He served a single term.^[1]

Hart was a prominent figure in the California phase of the Mystery airship wave of 1896–97, claiming to represent the airship's inventor.^{[citation needed]}

Hart married Loretta B. They had a son, Lowell J.^[2]

Hart died of the Spanish flu on December 24, 1918, aged 70 or 72, at his home in Palo Alto near El Palo Alto.^[2][1] He was buried at Cypress Lawn Cemetery.^[2]