Vatican I was an important council of the Roman Catholic Church held in the Vatican from 1869 to 1870. It was primarily concerned with clarifying the Church's understanding of its own authority and infallibility. There are several synonyms for Vatican I that can be used depending on the context. These include the First Vatican Council, the Council of the Vatican, and the Vatican Council of 1869-1870. Regardless of the terminology used, the importance of Vatican I in shaping the modern Catholic Church cannot be overstated. Its teachings continue to guide the faith of millions of Catholics around the world.