The Meduxnekeag River (muh-DUHKS-nuh-keg) is a small river in western New Brunswick, Canada. It is 35 miles (56 km) long.

It rises in Aroostook County in the State of Maine and flows to its end through the Town of Woodstock.

The North and South branches rise in east-central Maine; then flow approx. 20 miles (32 km) to a junction 8 miles (12.9 km) northeast of Houlton (on the South Branch), in N.B., then approx.15 miles (24 km) southeast to the junction with the St. John river at Woodstock.

In New Brunswick, the watershed of the Meduxnekeag is home to the richest, most diverse, and highest concentration of remnant sites of mature Appalachian Hardwood Forest in Atlantic Canada, containing many understorey plants rare or uncommon in the province. These include black raspberry, wild ginger, maidenhair fern, showy orchis, wild coffee, and numerous others. The non-profit Meduxnekeag River Association, based in Woodstock, has purchased, since 1998, approximately 120 hectares (290 acres) of forest, with more than 4 km (2.5 miles) of undeveloped shoreline. This Meduxnekeag Valley Nature Preserve has more than 10 km (6.25 miles) of well-marked, low impact walking trails.

Significant sections of the Meduxnekeag are easy to canoe or kayak in high or medium water conditions (generally in May and June, and in September and October; also in July/August in wet summers). Annual canoe races are held in both Maine and New Brunswick in May. Recreational canoeists traditionally put in just below the bridge on the North Branch (just above the confluence) and take out in downtown Woodstock, a half-day canoe depending on lingering time, passing through scenic, mostly forested country. The final 2 km before Woodstock is through an extensive wetland.

The intervales and islands of the Meduxnekeag are locally celebrated for the edible fiddlehead ostrich fern, harvested in May.