Aderno (anc. Adranum), a town of Sicily, in the government and 17 m. N. W. of Catania; pop. in 1861,12,877. It is situated on a plateau at the S. W. foot of Mt. Etna, and is approached by a steep winding road of 4 m. A large proportion of the inhabitants are monks and nuns. There are many remains of the ancient town and ruins of mediaeval buildings; and in the piazza is a Norman castle, now used as a prison.