Joseph René Vilatte, also known as Mar Timotheus I, was a French–American Catholic active in France and the United States. He was associated with several Christian denominations before his ordination in the Christian Catholic Church of Switzerland (CKS) bishop at the request of an Episcopal Church (USA) bishop for service in an Episcopal diocese. Eventually, he was reconciled with the Catholic Church and voluntarily entered a solemn vow of abjuration.

The terms Old Catholic Church, Old Catholics, Old-Catholic churches, or Old Catholic movement, designate "any of the groups of Western Christians who believe themselves to maintain in complete loyalty the doctrine and traditions of the undivided church but who separated from the see of Rome after the First Vatican council of 1869–70". The expression Old Catholic has been used from the 1850s by communions separated from the Roman Catholic Church over certain doctrines, primarily concerned with papal authority and infallibility. Some of these groups, especially in the Netherlands, had already existed long before the term. The Old Catholic Church is separate and distinct from Traditionalist Catholicism.