The Grand River is the longest river in the state of Michigan. It runs 260 miles through the cities of Jackson, Lansing, Grand Rapids, and Grand Haven, and the counties of Hillsdale, Jackson, Ingham, Eaton, Clinton, Ionia, Kent, and Ottawa before emptying into Lake Michigan.

Historically it has been a source of water for public consumption and manufacturing, a highway for moving goods, and a popular recreational asset.

Its watershed drains an area of 5,572 square miles. It has several dams along its length but is a trout and salmon stream for much of its length. Much of the basin is flat and it contains many swamps and lakes. Nevertheless, there is an elevation difference of 700 feet (213 m) between the source and mouth of the river.

Tributaries are the Red Cedar River, Looking Glass River, Maple River, Flat River, and the Thornapple River.