The First Vatican Council was an ecumenical council of the Catholic Church. It was held in Rome in 1869 and 1870. Its main result was that it said that popes are infallible: they are always right in matters of religion. The council is sometimes called Vatican I. This is because there also is a Second Vatican Council, or Vatican II. That council was held roughly 100 years later.

The First Vatican Council caused many issues: especially in Austria, Germany and Switzerland there were many Catholics that were very liberal. The did not like the idea that the pipe was now infallible. Also, there was a movement called the Old Catholic Church which formed and split: they do not think popes are infallible.