Oliver Sylvain Baliol Brett, 3rd Viscount Esher, GBE, FRSL, FRIBA (23 March 1881 – 8 October 1963) was a British peer and politician.

[1] Brett was the elder son of the Liberal courtier and politician Reginald Brett, 2nd Viscount Esher, the Governor of Windsor Castle, and Eleanor Van de Weyer, daughter of Belgian ambassador Sylvain Van de Weyer and grand-daughter of Anglo-American financier Joshua Bates.

[1] He was also involved with many cultural and artistic charities, including the Society for the Protection of Ancient Buildings, the London Museum, the Historic Churches Trust, and the Old Vic.

Oliver Brett was married to the American-born Antoinette Heckscher (1884–1967) at Wincoma, the country home of her parents in Huntington on Long Island in New York.

[13] After their marriage, the couple first made their home at Orchard Lea, Windsor Forest,[10] until acquiring the Watlington Park country house in the Chilterns in 1920.