The patron saint of Casale Monferrato is Saint Evasius, bishop of Asti, who converted the borough of Casale to Christianity and founded there the church of San Lorenzo, built on the site of today's cathedral; he is celebrated on 12 November.
The name Casale first appears in a donation document dated 15 August 988, addressed to the canonry of Sant'Evasio. According to the Passio describing his life and martyrdom, the church's foundation would date back as far as the 8th century, the work of the Lombard king Liutprand; in 1474, through a bull of Pope Sixtus IV, the church of Sant'Evasio was raised to cathedral status, the diocese of Casale was born and the borough was raised to city rank. The cathedral, today the town's oldest monument and one of Piedmont's most important Lombard Romanesque cathedrals, holds on the sarcophagus containing the saint's relics one of the oldest written records of Piedmontese vernacular, the inscription «Qual'è l'arca de San Vas», meaning «here is the sarcophagus of Saint Evasius».
