​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 rather over 4 m., but two promontories projecting from opposite shores about the centre narrow it to less than 1 m. On the south a passage so narrow as to be bridged communicates with Lough Cullin; the current through this channel, normally from Conn to Cullin, is sometimes reversed. The total length of the two loughs is nearly 12 m. They drain eastward by a short channel tributary to the Moy, and the principal affluents are the Deel and the Manulla. Lough Conn lies 42 ft. above sea-level. It contains a few islands, and its shores are generally low, but the isolated mass of Nephin (2646 ft.) rises finely on the west. The lake is in favour with anglers.