| Marshepaug River | |
| Name Other: | (Also called Ackerman Brook, Great Pond River, Marshapogge River, Mashepaug River, and other names) |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | States |
| Subdivision Name2: | Connecticut |
| Subdivision Type4: | Towns |
| Subdivision Name4: | Goshen, Litchfield |
| Length: | 3miles |
| Source1: | Woodbridge Lake |
| Source1 Location: | Goshen, Massachusetts |
| Source1 Coordinates: | (41.7981°N -73.2535°W) |
| Source1 Elevation: | 1138feet |
| Mouth: | East Branch of the Shepaug River |
| Mouth Location: | Litchfield, Connecticut |
| Mouth Coordinates: | (41.767°N -73.2776°W) |
| Mouth Elevation: | 978feet |
| River System: | Housatonic |
| Basin Size: | 7291.86acres |
| Custom Label: | Gradient |
| Custom Data: | 52.66 fpm |
The Marshepaug River is a 3adj=midNaNadj=mid stream in the towns of Goshen and Litchfield in northwest Connecticut in the United States. The river rises near the southwest corner of Woodbridge Lake and then flows in a southwest direction through the Milton Center Historic District to its mouth on the East Branch of the Shepaug River. It drains an area of more than and has a gradient of over 52 feet per mile.
During the 19th century, the river provided waterpower for sawmills, gristmills, bloomery forges, and other industries.