Casalmaggiore (Casalasco-Viadanese: Casalmagiùr) is a comune in the province of Cremona, Lombardy, Italy, located on the Po River.

Sights include the Duomo (cathedral), the Museo Diotti, and the Bijoux Museum.

Archaeological findings in 1970 proved that the area was inhabited from the Bronze Age, although the town most likely was founded by the Romans as Castra Majora ("Main Military Camp").

Around the year 1000 it was a fortified castle in the House of Este lands; in the 15th century it was under the Republic of Venice.

After a period under the Austrians, it became part of the newly unified Kingdom of Italy in 1861.