Algernon St. Maur, 15th Duke of Somerset, etc. (22 July 1846 – 22 October 1923, in Maiden Bradley) was the son of Algernon St. Maur, 14th Duke of Somerset and Horatia Morler. He was also a baronet.

On September 5, 1877, he married Susan Margaret Richards Mackinnon, the ninth daughter of Charles Mackinnon of Corriechatachan, but the marriage was childless.

He was educated at Britannia Royal Naval College, but later joined the 60th Rifles and took part in the Wolseley Expedition of 1870. He was a tall and athletic man, of powerful build. After leaving the Regular Army, he spent several years ranching in Western America. On accession to the Dukedom in 1894, he voted often in the House of Lords, although he seldom spoke there. He became president of Dr Barnardo's Homes, a charity which both he and the Duchess had supported for many years.^[1]

Somerset took a long lease of No. 35 Grosvenor Square, Mayfair in 1898,^[2] which he maintained as his London residence until his death in 1923. He bequeathed his lease of 35 Grosvenor Square and a life annuity of £4,000 to his widow Susan, Duchess of Somerset,^[3] and she continued to live at 35 Grosvenor Square until early 1934,^[4][5] after which she leased No. 30 Grosvenor Square until her death in 1936.^[6][7]

When Somerset died in 1923, he left no son, and his brothers Lord Ernest and Lord Edward had both recently died childless, so his titles and estates were inherited by the nearest heir, his distant cousin Colonel Edward Seymour.

The Duke was buried on Brimble Hill Clump near his main residence at Bradley House, Maiden Bradley, Wiltshire. His widow was also buried there when she died in 1936. Their graves are in a little wood on a hilltop surrounded by agricultural land, with a metal fence around them, and marked by standing rough stones with small text plaques.^[8]