Download coordinates as: La Moine River is a 125-mile-long (201 km)[2] tributary of the Illinois River in western Illinois in the United States.

Its watershed covers approximately 2,000 square miles (5,000 km2), and it is the sixth-largest tributary to the Illinois River.

In its lower course the river passes the village of Ripley and is used to define a portion of the boundary between Schuyler and Brown counties.

It flows into the Illinois River from the northwest, about 4 miles (6 km) southwest of Beardstown.

In its headwaters region the river collects the short South Branch La Moine River, which rises in McDonough County and flows west-southwestwardly into Hancock County, past La Harpe.