The Oxoboxo River, shown on federal maps as Oxoboxo Brook, is a tributary of the Thames River in New London County, Connecticut. It flows roughly in a southeasterly direction from its source at Oxoboxo Lake to its confluence with the Thames. It has a watershed of , 87% of which is in the town of Montville.
The Oxoboxo was an important source of water power during English colonial settlement and 19th-century industrial development in Montville. The first sawmill on the river was established in 1653. As of the 1880s, the river supplied power for 15 cotton, woolen, and paper mills. The river's source, Oxoboxo Lake, is a natural lake whose size and elevation have been increased by damming. The earliest dam at Oxoboxo lake was constructed in the 1600s; it has been rebuilt and increased in height several times since, reaching its current elevation in the 1880s.
The name was derived from Native American terms for the river and lake. Other historical names for the stream and alternative spellings of "Oxoboxo" include Abscubogset, Absubogsuck, Cochikuack Brook, Cokichiwake, Cokikuak, Cuchickuwock, Okeshoksee, Okseboksce, Oxopaugsuck, Oxyboxy, and Sawmill Brook. Many are transliterations of the feature name in the Mohegan and other Algonquian languages of historical Native American tribes in the area.