A river of Scotland whose drainage area lies almost wholly within Perthshire; rises on the northern slope of Ben Lui, on the Argyll and Perthshire border, and flowing 25 m. NE. under the names of Fillan and Dochart, enters Loch Tay, whence it sweeps N., SE., and E., passing Aberfeldy, Dunkeld, Perth, and Dundee, and enters the North Sea by a noble estuary 25 m. long and from ½ m. to 3½ m. broad; chief affluents are the Tummel, Isla, Almond, and Earn; discharges a greater body of water than any British stream; is renowned for the beauty of its scenery, and possesses valuable salmon fisheries; has a total length of 120 m., and is navigable to Perth; immediately W. of Dundee it is spanned by the Tay Bridge, the longest structure of its kind in the world, consisting of 95 spans, with a total width of 3440 yards; Loch Tay, one of the finest of Highland lochs, lies at the base of Ben Lawers, stretches 14½ m. NE. from Killin to Kenmore, and varies from ½ m. to 1½ m. in breadth.