CASTLEBAR, a market town and the county town of Co. Mayo, Ireland, in the west parliamentary division, on the river and near the lough of the same name, on the Manulla and Westport branch of the Midland Great Western railway. Pop. of urban district (1901) 3585. The county court buildings and other public offices occupy a square, and there is a pleasant mall shaded by fine trees. There are some breweries, and trade in linens and agricultural produce. The castle, which gives its name to the town, was a fortress of the De Burgh family; but the town itself was founded in the reign of James I., and received a charter from him in 1613. In 1641 the castle was held for the parliament by Sir Henry Bingham, but he was forced to surrender to Lord Mayo, and fell a victim, with all his garrison, to the fury and treachery of the besiegers. The massacre was afterwards avenged in 1653 by the execution of Sir Theobald Burke (by that time Lord Mayo), who had been in command along with his father at the siege. In 1798 the town was occupied for some weeks by the French under General J. J. Humbert, who had defeated the English under Luke Hutchison in a conflict which is jocularly styled the “Castlebar Races.” The town returned two members to the Irish parliament until the Union. Four miles N.E. of Castlebar is Turlough, with a round tower 70 ft. high and 57 ft. in circumference, and other remains.