Monadhliath Mountains, mountain range in the Highland council area, Scotland, between Loch Ness in the northwest and the River Spey in the southeast. The range has several summits with elevations greater than 3,000 feet (900 metres), the highest being Carn Mairg at 3,087 feet (941 metres), the haunt of eagles and wild cats. The River Findhorn rises on the northwestern slopes of Carn Mairg and flows northward to the North Sea.