CONN, LOUGH, a lake of western Ireland, in Co. Mayo. Its length (N.N.W. to S.S.E.) is 9 m. and its extreme breadth 5 m. On the south a narrow passage communicates with Lough Cullin. The total length of the two loughs is nearly 12 m. They drain eastward by a short channel tributary to the Moy. Lough Conn lies 42 ft. above sea-level. It contains a few islands, and its shores are generally low.