John McDermeid Gearin (August 15, 1851 – November 12, 1930) was an American politician and attorney from the state of Oregon. A native of the eastern portion of the state, he represented Portland on the western side of the state in the Oregon House of Representatives. Originally an independent politician, he later became a Democrat and lost an election to serve in the United States Congress before winning appointment to the Senate in 1905. He also was Portland's city attorney and a district attorney.