The Grass River is a short river in Antrim County in the U.S. state of Michigan. It is part of a watershed that begins in northern Antrim County with Intermediate Lake, which is connected by the Intermediate River with Lake Bellaire. The Grass River flows from Lake Bellaire into Clam Lake, which in turn drains into Torch Lake via the short Clam River. Torch Lake itself is drained by the Torch River, which flows into Lake Skegemog, which opens into Elk Lake. Elk Lake flows into the east arm of Grand Traverse Bay at Elk Rapids.