Sylvia Leonora Brett, 25 February 1885 – 11 November 1971), was an English aristocrat who became the consort to Sir Charles Vyner de Windt Brooke, the third and last of the White Rajahs of Sarawak.

1 Tilney Street, Park Lane,[citation needed] Central London, the second daughter of Reginald Baliol Brett, the 2nd Viscount Esher, KCB.

Her mother Eleanor was the third daughter of the Belgian politician and revolutionary Sylvain Van de Weyer and his wife Elizabeth, who was the only child of the great financier Joshua Bates of Barings Bank.

[3] She first visited Sarawak in 1912,[3] where her husband-to-be (from 1917) ruled a 40,000-square-mile (100,000 km2) jungle kingdom on the northern side of Borneo with a population of 500,000, an ethnic mix of Chinese, Malays, and the headhunting Dayak.

Brett was distraught that her eldest daughter, Leonora, under Islamic law, could not take the throne; as a result she hatched various plots to blacken the name of the heir apparent, Anthony, the Rajah Muda.