Leitrim (Irish: Liatroim) is a barony in Ireland that lies partly in County Galway and partly in County Clare.^{[la 1]} It is located in the south-eastern corner of County Galway and the north-eastern corner of County Clare. Prior to 1898, the entire barony was contained in County Galway. The Local Government (Ireland) Act 1898 split the barony: part of the barony was transferred to County Clare. Leitrim is bounded, clockwise from the southwest, by the Clare baronies of Tulla Upper and Tulla Lower; the Galway baronies of Loughrea to the west, Kilconnell to the north, and Longford to the east; and by Lough Derg to the south and southeast.^[1] It measures 20 miles (32 km) from north to south and 9.5 miles (15.3 km) from east to west.^[2]

The highest peak in the barony is the Scalp (380m), part of the Slieve Aughty range. Lough Derg forms the barony's eastern boundary. Three rivers flow in an easterly direction to the Lough; from north to south they are the Cappagh, the Woodford, and the Coos. The mines at Tynagh were a source of lead and zinc from the 1960s until their closure in 1981.^{[citation needed]}

The R353 regional road bisects the barony from east to west. At the northern end is the N65 national road.

Settlements in the barony include Caherakilleen,^{[la 2]} Kilreekill, Tynagh and Woodford in Galway, and Mountshannon and Whitegate in Clare.