The Grand River (Ottawa: Owashtanong, "Far-Flowing Water") is a river in the southwestern portion of the southern peninsula of Michigan, United States, that flows into Lake Michigan's southeastern shore. It is the longest river in Michigan, running 252 miles (406 km) from its headwaters in Hillsdale County on the southern border north to Lansing and west to its mouth on the Lake at Grand Haven.

The so-named Grand Rapids, in what is today the namesake city, were a mile-long, 300-yard-wide and 10-to-15-foot-tall rapids for which the river was famous. These were submerged following the construction of numerous dams, starting in 1835, and flooding of areas behind the dams. The river has not had any rapids for nearly a century.