The West Branch Oyster River is a 3.3-mile-long (5.3 km) tributary of the Oyster River in Warren, Maine. From its source (44°08′57″N 69°12′47″W / 44.1492°N 69.2131°W), the stream runs about 2 miles south and 1 mile east to its confluence with the main stem of the Oyster River.