The Margaret River is a river in southwest Western Australia. In a small catchment, it is the eponym of the town and tourist region of Margaret River.The river arises from a catchment of just 40 square kilometres in the Whicher RangeThe middle reaches passes through land cleared for agriculture, especially viticulture.There is a weir across the river just above the town. The mouth of the river is a small estuary, closed to the ocean by a sandbar that opens only seasonally.Margaret River is presumed to be named after Margaret Wyche, cousin of John Garrett Bussell (founder of Busselton) in 1831.