Tayside was one of the nine regions used for local government in Scotland from 16 May 1975 to 31 March 1996. The region was named for the River Tay.

The River Tay is the longest river in Scotland and the seventh-longest in Great Britain. 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 United Kingdom by measured discharge. Its catchment is approximately 2,000 square miles, the Tweed's is 1,500 sq mi (3,900 km2) and the Spey's is 1,097 sq mi (2,840 km2).