Michael John MacMahon (8 March 1854 – 11 July 1931) was an Australian politician.
He was born in Morpeth to Denis MacMahon and Bridget Cahill.
Educated in Maitland, he established a local store at Urala, where he was an alderman (1882–1900) and mayor (1884, 1887, 1890–91, 1897–1900).
On 7 September 1887 he married Martha Mary McCrossan, with whom he had five children.
In 1900 he won a by-election for the New South Wales Legislative Assembly seat of Uralla-Walcha as a Protectionist.