The Battle of Marciano (also known as the Battle of Scannagallo) occurred in the countryside of Marciano della Chiana, near Arezzo, Tuscany, on August 2, 1554, during the Italian War of 1551. The battle marked the defeat of the Republic of Siena in its war against the Duchy of Florence, and resulted in Siena losing its independence and being absorbed into the Grand Duchy of Tuscany.