Mariano Téllez-Girón y Beaufort Spontin, 12th Duke of Osuna, GE, OM, LH, OAN, KA, was a Spanish peer, diplomat and army officer, whose lavish exploits as Ambassador of Spain to the Russian Empire earned him admiration and popularity amongst European courts. He was a younger brother of Pedro de Alcántara Téllez-Girón, from whom he inherited his 59 peerage titles when he died prematurely in 1844.
- Occupation
- diplomat, politician, military personnel, art collector
- Position held
- Senator for Life of Spain, Spanish ambassador to the Russian Empire, Gentilhombre de cámara con ejercicio, member of the Cortes during the reign of Isabel II
- Citizenship
- Spain
