Leopoldo O'Donnell y Jorris, 1st Duke of Tetuán, GE (12 January 1809 – 5 November 1867), was a Spanish general and Grandee who was Prime Minister of Spain on several occasions.

He was of distant Irish paternal ancestry, the 11th generation descendant of Calvagh O'Donnell, Rí of Tír Chonaill,[2][3] a Gaelic territory in the west of Ulster in the north of Ireland.

Espartero relinquished power in O'Donnell's favour on 14–15 July 1856, and Queen Isabella II asked him to form a government as the 44th Prime Minister of Spain.

[6] For his new administration, O'Donnell formed the Unión Liberal Party, which was designed to combine Progressive, Moderate, and Carlist factions.

O'Donnell attempted to define moderate policies for Spain with this new party, advocating a laissez-faire approach and confiscating church land.

He was a proponent of a new and aggressive imperial policy, intended principally to expand Spanish territory in Africa, particularly after French successes in Algeria.