Leopold O'Domell (Span. O'Donel, Leo-poldo), count of Lucena and duke of Tetuan, a Spanish soldier, born in Santa Cruz, island of Teneriffe, Jan. 12, 1809, died at Biarritz, France, Nov. 5, 1867. He was the son of a Spanish general who was descended from an Irish family that emigrated after the battle of the Boyne. Leopold entered the army, and at the age of 23 attained the rank of colonel. The Carlist war, in which he sided with the young queen, first brought him prominently into notice; and for his services in raising the siege of Lucena he was created count, and received the command of the army of the centre. He subsequently attached himself to the cause of the queen mother Christina, with whom, on the elevation of Espartero to the regency, he was obliged to take refuge in France. In 1841 he was permitted to return to Spain upon pledging his fealty to the government; but he almost immediately headed an insurrection in Navarre. Defeated at Pamplona, he again fled to France. On the overthrow of Espartero in 1843 he returned to Spain, and was appointed captain general of Cuba, where he is said to have amassed a fortune.

After his return from Cuba he busied himself again with political intrigues, and on threatening to exert his influence against the government was appointed by Narvaez director general of the infantry, which office he retained till 1851. During the Sartorius ministry he became so deeply implicated against the court and Queen Christina, that at the commencement of 1854 he was proscribed; but in June he headed a revolt and fought an indecisive battle at Vical-baro. He then effected a union with theprogre-sista party, and issued a manifesto demanding the restitution of the constitution of 1837, the emancipation of Queen Isabella, the perpetual banishment of the queen mother, the amelioration of the laws regulating the elections and the press, the reduction of taxes, and other popular measures. At this crisis Espartero was invited by the queen to form a ministry, and O'Donnell received the portfolio of the war department, and was appointed a marshal. In July, 1856, he succeeded Espartero as president of the council, and at once declared Spain under martial law, closed the cortes, and abolished the national guard.

Insurrections followed, which were generally suppressed; but Narvaez plotted against him, and obliged him to resign in October. lie returned to power in 1858, and in 1859 was at once prime minister and commander-in-chief of the forces engaged in the war in Morocco. For his services in the latter, which was decided by the victory at Tetuan and the surrender of that city (February, 1860), he was created duke. In February, 1863, he resigned, but was recalled in June, 1865. He now endeavored to restore tranquillity and to carry out many reforms, and procured the acknowledgment of the kingdom of Italy notwithstanding the opposition of the court. The extremists of all parties united against him. Insurrections were frequent, and much blood was shed in suppressing them. In July, 1866, the queen called upon Narvaez to form a new ministry from the reactionary party. O'Donnell went to France, and remained there until his death.