The River Tay is the longest river in Scotland and the seventh-longest in the United Kingdom. The Tay originates in western Scotland on the slopes of Ben Lui, then flows easterly across the Highlands, through Loch Dochart, Loch Iubhair and Loch Tay, then continues east through Strathtay, in the centre of Scotland, then southeasterly through Perth, where it becomes tidal, to its mouth at the Firth of Tay, south of Dundee. It is the largest river in the UK by measured discharge. Its catchment is approximately 2,000 square miles, the Tweed's is 1,500 square miles and the Spey's is 1,097 square miles.
The river has given its name to Perth's Tay Street, which runs along its western banks for 0.47 miles.