Mathieson Harry Jacoby (1 July 1869 – 3 April 1915) was an Australian politician who twice represented the seat of Swan in the Legislative Assembly of Western Australia, from 1901 to 1905 and then again from 1908 to 1911. He was Speaker of the Legislative Assembly from 1904 to 1905. Outside politics Jacoby was a noted viticulturist, one of the pioneers of the West Australian wine industry.