William Irwin (July 12,[citation needed] 1827 – March 15, 1886) was an American politician from the Democratic Party who served as the 13th governor of California between 1875 and 1880.

He previously served as acting lieutenant governor for nine months in 1875.

After moving to California, Irwin worked in various private industries and in 1865 was a candidate for Siskiyou County Tax Collector but lost.

[1] He was eventually elected to the California State Assembly, representing the 28th district.

[2] Irwin was the one who appointed young journalist Henry George to the office of State Inspector of Gas Meters in 1876, which lifted George and his family out of destitution and allowed him to write Progress and Poverty.