Well-educated deacon in the archdiocese of Milan, Italy. Taught at the cathedral school of Milan. Led the Pataria, the anti-nicolaism and anti-simony efforts in Milan, begining in 1057. He had the support of the Vatican, but was opposed by his simoniac archbishop Guido da Velate. More than just a theological argument, the dispute led to violence. Arialdus went into hiding outside the city, Pope Alexander II excommunicated the archbishop who then had Arialdus arrested, imprisoned and executed. Martyr.
- 1066 at a castle on a small island in Lago Maggiore near Milan, Italy
- re-interred in a monastery in Milan in 1067
- “Saint Arialdus of Milan“. CatholicSaints.Info. 21 June 2015. Web. 23 October 2016. <>