Leitrim (lēˈtrĭm) [key], county (1991 pop. 25,301), 589 sq mi (1,526 sq km), N Republic of Ireland. The county seat is Carrick-on-Shannon. Leitrim is divided into two parts by Lough Allen; the northern part is mountainous, the southern part level. Potatoes and oats are grown. Industries include textiles, electrical goods, and automotive parts. The population declined by more than 100,000 through the 20th cent.