Mathieson Harry Jacoby[a] (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.

In 1893, assisted by their father, he and his two brothers (Frederick and Ted) bought a vineyard in the Perth Hills, abutting the Smiths Mill line of the Eastern Railway.

He had first become involved in public life shortly after arriving in Western Australia, when he and George McWilliams established the first branch of the St John Ambulance in the colony.

[1] Jacoby's candidacy was endorsed by The Sunday Times, who regarded him as "a clean citizen and a trustworthy politician with a democratic programme", and also noted that he had "won the confidence of the Labor Party".

[10] The Sunday Times, which had earlier praised Jacoby, accused him of "buying votes with beer",[11] and expressed that he had "unquestionably disgraced the Parliament" and proved his "unfitness for membership".

Jacoby, supported by Labor, was elected "by a large margin" over John Foulkes, who was the candidate of the government of Walter James (recently reduced to a minority in the assembly).

Jacoby's election was regarded with bemusement, although not unfavourably received, by The West Australian,[4] but was condemned completely by The Sunday Times, which wrote that he was "of all men the least fitted by nature, ability and training for the responsible post into which accident has exalted him".