| La Moine River | |
| Source1 Coordinates: | 40.6412°N -90.759°W |
| Mouth Coordinates: | 39.9873°N -90.514°W |
| Progression: | La Moine River → Illinois River → Mississippi River → Gulf of Mexico |
| Mouth Elevation: | 440feet |
| Length: | 125miles |
| Discharge1 Avg: | 884 cu/ft. per sec.[1] |
| Custom Label: | GNIS ID |
La Moine River is a 125adj=midNaNadj=mid[2] tributary of the Illinois River in western Illinois in the United States. Its watershed covers approximately 2000sqmi, and it is the sixth-largest tributary to the Illinois River.[3] It is part of the watershed of the Mississippi River.
La Moine River rises in southwestern Warren County and initially flows southwestwardly through southeastern Henderson and northwestern McDonough counties into Hancock County, where it turns to the southeast and flows through McDonough and Schuyler counties. 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 4miles 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. In Hancock County it collects the East Fork La Moine River, which rises in Warren County and flows south- and southwestwardly through McDonough County, past Macomb.
The United States Board on Geographic Names settled on "La Moine River" as the river's official name in 1933. According to the Geographic Names Information System, the river has also been known as: