The Grand River is a 252-mile-long (406 km) river in the Lower Peninsula of the U.S. state of Michigan. The longest river in Michigan, the Grand River rises in Hillsdale County, and flows in a generally northwesterly direction to its mouth at Lake Michigan in the city of Grand Haven. The river flows through a number of cities, including Jackson, Lansing, Ionia, and Grand Rapids.

The Lower Peninsula of Michigan – also known as Lower Michigan – is the larger, southern and less elevated of the two major landmasses that make up the U.S. state of Michigan; the other being the Upper Peninsula, which is separated by the Straits of Mackinac. It is surrounded by water on all sides except its southern border, which it shares with Indiana and Ohio. Although the Upper Peninsula is commonly referred to as "the U.P.", it is uncommon for the Lower Peninsula to be called "the L.P."