Jan Kowalski, later known as Maria Michał Kowalski (27 December 1871 – 18 May 1942), was a Polish Roman Catholic diocesan priest who became a schismatic religious leader and controversial innovator. Following excommunication from his church, he was consecrated as a bishop in the Old Catholic Archdiocese of Utrecht, established the Old Catholic Church of the Mariavites in Poland, rose to be its archbishop and died a martyr. He is venerated as a saint in the Catholic Mariavite Church.