CASTLEBAR, urban district and county town of Co. Mayo, Ireland, on the river and near the lough of same name. Pop. (1926) 4,256. The castle belonged to the De Burgh family but the town was founded in the reign of James I. and received a charter in 1613. In 1641 the castle fell to the royalists. The town was held for a short period in 1798 by the French. Four miles north-east is a round tower 7o ft. high and 57 ft. in circumference. Trade is in linen goods and agricultural produce.