I would like to know if Catholism is the oldest religion.
Although the Church as we know it today did not become “visible” until the day of Pentecost shortly after Jesus’ resurrection, the Church was in formation from the beginning of time. The Catechism of the Catholic Church (CCC) explains, “[A]lready present in figure at the beginning of the world, this Church was prepared in marvelous fashion in the history of the people of Israel and the old Alliance. Established in this last age of the world and made manifest in the outpouring of the Spirit, it will be brought to glorious completion at the end of time” (CCC 759).
For more on this see The Church’s Origin, Foundation, and Mission (scroll down).