William Henry Harrison Hart (January 25, 1846/1848 – December 24, 1918) was the 16th California Attorney General.

Prior to this position, Hart claims to have been a United States Secret Service agent and to have fought in the American Civil War.

Hart struggled through a difficult childhood which led to his desire for danger and his allegedly joining the United States Secret Service at the age of only 14.

[1][clarification needed] Hart once claimed to have received the highest fee ever paid to a lawyer for a single case in the United States.

[2] A victim of the 1918 Spanish flu pandemic, Hart died on December 24, 1918, aged 70 or 72, at his home in Palo Alto, California.