The river rises in the Mamores mountain range approximately halfway between Ben Nevis and Loch Treig, 370m above sea level. In its upper reaches it is known as Water of Nevis, becoming River Nevis at the bridge near Achriabhach. It is partly fed by the Steall Waterfall, one of the highest waterfalls in Scotland. The river flows through Glen Nevis and on to the town of Fort William where it is crossed by the Nevis Bridge on the A82 road. Its mouth is at the sea loch of Loch Linnhe where it meets the sea within the estuary of the River Lochy.