Edward Douglas John Hay, 13th Marquess of Tweeddale (6 August 1947 – 1 February 2005), was a Scottish peer, a member of the House of Lords.

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Hay was the elder of twin sons of David Hay, 12th Marquess of Tweeddale (1921–1979), and his first wife, Sonia Peake, daughter of Osbert Peake, 1st Viscount Ingleby. He was educated at Milton Abbey and Trinity College, Oxford, where he graduated BA. He became an insurance broker before succeeding his father in the marquessate and its subsidiary titles, and also as Hereditary Chamberlain of Dunfermline.

He rarely spoke in the House of Lords, but achieved fleeting prominence during the Bosnian War debate on 28 October 1996^[1] and in a subsequent letter to The Times on the subject.

Tweeddale died unmarried on 1 February 2005, aged 57, and was succeeded by his younger twin brother Lord Charles Hay, thus becoming one of the few British peers to be succeeded by a younger twin. The next heir is their youngest brother Lord Alistair Hay, styled Master of Tweeddale as heir presumptive.

Since none of the three brothers, the sons of the 12th Marquess's first marriage, married, the next in succession are their two half-brothers, sons of the 12th Marquess's second marriage. The two half-brothers are also twins, but the older of the two, Lord Andrew Arthur George Hay, is the only one to be married with children.

The 13th Marquess is remembered chiefly for being one of the few British peers to be succeeded by a younger twin brother. Similarly, the 3rd Earl of Durham (1855–1928) was succeeded in 1928 by his younger twin brother, the 4th Earl (1855–1929). The 3rd Viscount Knutsford (1855–1935) also succeeded an older twin, the 2nd Viscount (1855–1931 dspm) on 27 July 1931.

Although the 3rd Marquess of Linlithgow and the 1st Baron Glendevon (formerly Lord John Hope) were twins, both were succeeded by their sons.