The Erro (in Piedmontese Er) is a 46-kilometre (29 mi) torrent of north-west Italy, a right tributary of the Bormida.

Having passed through the territory of Sassello, the river enters the Piedmontese Province of Alessandria at Ponte Erro (Malvicino).

Its course takes it past Cartosio, Rivere, Castelletto d'Erro, Arzello, and Melazzo before joining the Bormida at Terzo, a little upstream from Acqui Terme at an elevation of 222 metres (728 ft).

The initial version of this article was a translation from it:Erro (torrente), its counterpart in the Italian Wikipedia.

Media related to Erro (stream) at Wikimedia Commons