Castelfidardo (Marchigiano: Castello) is a town and comune in the province of Ancona, in the Marche region of central-eastern Italy.

It is particularly remembered for a Sardinian victory over a papal army composed of foreign volunteers defending the Papal States, on September 18, 1860. The town's Museum of the Risorgimento, in the palazzo Mordini, commemorates the battle and places it in the wider context of the Risorgimento as a whole. It houses artifacts and documents of the period, including around 130 loans from private collections or other museums.