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 6 miles (9.7 km) in a southeasterly direction from its source at Oxoboxo Lake to its confluence with the Thames. It has a watershed of 6,768 acres (27.39 km2), 87% of which is in the town of Montville.