O'NEILL DE TYRONE, Arthur, Marquis del Norte, Spanish soldier, born in Dublin, Ireland, 8 January, 1736; died in Madrid, Spain, 9 December, 1814. He emigrated with his parents to Spain when he was a boy, and began his military career in 1752 as a cadet in the Irish infantry regiment. He took part in 1762 in the campaign in Portugal and the expedition to Algiers. At the beginning of next year he volunteered for the expedition to Brazil under General Cevallos and led a hazardous attack on Fort Santa Cruz in the island of Santa Catharina, of which he was appointed governor. Toward the end of that year he volunteered again for the expedition to Martinique under General Navia, which was frustrated by the dispersion of the feet in a storm, and later he went with Bernardo de Galvez (q. v.) to Louisiana. He accompanied the latter in the siege of Pensacola in 1781, repelled several sallies of the garrison, and after the surrender of the city on 9 May was appointed its governor, which post he occupied till 10 December, 1793, when he was appointed captain-general of the province of Yucatan. He planned and commanded in 1798 the expedition against Belize and the English possessions in the Bay of Honduras. At his request he was relieved in 1802, and in the next year he was appointed a member of the supreme military court. In 1808, during the invasion of the French, notwithstanding his advanced age, he entered the service again, led the second division of the army of Old Casthe, and in the defence of Madrid commanded the batteries of the Gate de los Pozos.