The Des Moines River () is a tributary of the Mississippi River in the upper Midwestern United States that is approximately long from its farther headwaters. The largest river flowing across the state of Iowa, it rises in southern Minnesota and flows across Iowa from northwest to southeast, passing from the glaciated plains into the unglaciated hills near the capital city of Des Moines, named after the river, in the center of the state. The river continues to flow at a southeastern direction away from Des Moines, later flowing directly into the Mississippi River.