Mill Plain may refer to:
Mill Plain, Washington, an unincorporated area in Clark County, Washington, United States Mill Plain, Danbury, Connecticut, an unincorporated area in the City of Danbury, Connecticut, United States Mill Plain, Fairfield, Connecticut, a census-designated place in Fairfield County, Connecticut, United States Mill Plain station, a former rail station in Danbury, Connecticut, United States Mill Plain BRT, a bus rapid transit route in Vancouver, Washington, United States