Theresa Susey Helen Vane-Tempest-Stewart, Marchioness of Londonderry (née Chetwynd-Talbot; 6 June 1856 – 16 March 1919) was a British socialite and political hostess.

[2] She was the elder daughter of Charles Chetwynd-Talbot, 19th Earl of Shrewsbury and his wife Anna Theresa Cockerell (1836–1912).

[2] She married Charles Vane-Tempest, Viscount Castlereagh, later the 6th Marquess of Londonderry, in the private chapel of Alton Hall in 1875.

[1] At the end of 2023 the BBC launched the radio and podcast miniseries The Mystery of Mount Stewart, narrated by Kerri Quinn, about a boat that sank on Strangford Lough in April 1895.

Theresa, Lady Londonderry, had lend her sailing boat, as a treat to her senior servants, which she called friends.