Allendale is a census-designated place (CDP) in Ottawa County in the U.S. state of Michigan. The population was 17,579 at the 2010 census. It is located within Allendale Charter Township, occupying the northern two-thirds of the township, from the eastern boundary with the Grand River west along Pierce St., north along 75th Ave., then west along Lake Michigan Drive (M-45) to the western boundary of the township.