James Arthur Mathieu (– November 23, 1966) was an Ontario lumber merchant, philanthropist and political figure. He represented Rainy River in the Legislative Assembly of Ontario as a Conservative-Liberal and then Conservative member from 1911 to 1923 and 1926 to 1929.
Mathieu came to Rainy River from Minnesota around 1903 as a manager of a sawmill and later established his own lumber company. He set up an educational foundation to provide financial assistance for students from the area. Mathieu also established a wildlife reserve and help fund community projects in the region. During his time in the provincial assembly, he helped promote the development of roads to encourage settlement in the district.