The existence of God is not only an object of natural reason but also an object of supernatural faith.
Source in Latin:
Pius IX, Dogmatic Constitution “Dei Filius”, Session III (April 24, 1870), Chapter IV. In: Acta Sanctae Sedis, Vol. III (1870), pp. 578–584.
Systematic Source:
Denzinger-Schönmetzer DS 3015 / CCC Nos. 36-38 / CCC No. 50