Feliksa Magdalena Kozłowska, known by the religious name Maria Franciszka and the epithet "Mateczka", was a Polish religious sister, Christian mystic and visionary who founded a movement of renewal in the Roman Catholic church in the Russian Partition of Poland. It was to follow the simplicity of the life of Mary, mother of Jesus. Early in the 20th century, she and this movement were excommunicated and became an autonomous church in fellowship with the Old Catholic Church of the Netherlands. In 1935 it split in two and became the Old Catholic Mariavite Church and the Catholic Mariavite Church. Both denominations were part of a single schism from the Catholic Church which declared it as heretical in 1906.

The Old Catholic Mariavite Church refers to one of two independent Christian churches, both of which can be dated from 1906 but which became distinct post 1935 as a result of doctrinal differences, and are collectively known as Mariavites. Mariavitism first emerged from the religious inspiration of Polish noblewoman and nun Feliksa Kozłowska (1862-1921) living in the Russian Partition of Poland in the late 19th-century. A young Catholic priest from a modest background, Jan Maria Michał Kowalski (1871-1942), became convinced by Kozłowska's revelations and adopted her vision as his own project by her side.