Lady Myra Idina Sackville (26 February 1893 – 5 November 1955) was an English aristocrat and member of the Happy Valley set.

She was the daughter of Lady Muriel Agnes Brassey and Gilbert Sackville, Viscount Cantelupe (1869–1915), who in 1896 succeeded his father as the 8th Earl De La Warr.

She had two younger siblings, sister Lady Avice (wife of Sir Stewart Menzies) and brother Herbrand.

[5] In homage to her childhood home, Lady Idina designed Kildonan House, Barrhill, South Ayrshire with the architect James Miller.

[8] The Happy Valley set were a group of elite, colonial expatriates who became notorious for drug use, drinking, adultery and promiscuity.

She and her husband soon became a part of this group and accumulated debts leading to their subsequent divorce, brought on by him cheating her financially.

[9] They had one child together:[10] After their divorce, their daughter was taken home to England to be raised firstly by her uncle Herbrand Sackville, 9th Earl De La Warr, and then by her aunt Lady Avice Spicer in Wiltshire.

[17] On 22 November 1930, Lady Idina married Donald Carmichael Haldeman, at the Shoreham Register Office in Kent.