Ann Arbor Charter Township is a charter township of Washtenaw County in the U.S. state of Michigan. As of the 2000 census, the township population was 4,720. The city of Ann Arbor is adjacent to the township on the south and west sides. Small islands of the township also lie within the boundaries of the city of Ann Arbor. Over time, these areas are being annexed into the city of Ann Arbor. Under a 1994 boundary agreement with the city of Ann Arbor, eventually all of these islands will be permitted to be annexed by the city.