The Battle of Castlebar was a military engagement of the Irish Rebellion of 1798, which occurred on 27 August 1798 near the town of Castlebar, County Mayo. A combined force of approximately 800 French troops and 2,000 United Irishmen rebels, commanded by Jean Joseph Amable Humbert, routed a British Crown force numbering from 3,000 to 5,000 men, led by Gerard Lake, 1st Viscount Lake, in what would later become known as the "Castlebar Races" or "Races of Castlebar".