Thomas Preston, 1st Viscount Tara (1585October, 1655) was an Irish soldier of the 17th century. After lengthy service as a mercenary in the Spanish Army Preston returned to Ireland following the outbreak of the Rebellion of 1641. He was appointed to command the Leinster Army of the Irish Confederacy, enjoying some success as well as a number of heavy defeats such as the Battle of Dungans Hill in 1647 where his army was largely destroyed. Like other Confederate leaders, Preston was a Catholic Royalist. He remained in close contact with the Lord Lieutenant the Marquess of Ormonde, and was a strong supporter of an alliance between Confederates and Royalists against the English Republicans.