The Battle of Casalecchio took place on 26 June 1402 near the town of Casalecchio di Reno, near Bologna. At this battle, a Bolognese army under Giovanni I Bentivoglio opposed Gian Galeazzo Visconti, Duke of Milan, and his allies, the Malatesta of Rimini and the Gonzaga of Mantua. Bologna was aided by Florence in these cities' struggle to halt the expansion of Visconti's power. The Bolognese-Florentine army was under Muzio Attendolo.