The Margaree-Lake Ainslie system is the largest river system on Cape Breton Island, and one of the largest in Nova Scotia, with a total length of 120 km and a watershed of 1165 km2. The swift Northeast Margaree rises on the plateau of the rugged Cape Breton Highlands, while the Southwest Margaree slips and slides quietly out of Lake Ainslie, the largest natural freshwater lake in Nova Scotia. The 2 branches merge at Margaree Forks and the river continues northwards to the Gulf of St. Lawrence.
The Mi'kmaq called the river Weekuch. The early French name for Margaree Harbour was Havre de Madre or Magre, and 18th-century maps referred to the river as St Marguerite.
The Margaree is considered to be the best Atlantic salmon river in Nova Scotia. The icy clear waters of the wild upper reaches are a mecca for spawning Atlantic salmon and trout. Downstream, the river runs past fertile farms, weirs and villages rich in Acadian and Scottish heritage. In 1998 it became part of the Canadian Heritage Rivers System.