Romanus Pontifex (from Latin: "The Roman Pontiff") is a papal bull issued several times over the 15th century, first in 1436 by Pope Eugenius IV and again in 1455 by Pope Nicholas V to King Afonso V of Portugal. As a follow-up to the Dum Diversas, it confirmed to the Crown of Portugal dominion over all lands south of Cape Bojador in Africa, along with encouraging the seizure of the lands of Saracen Turks and non-Christians. The bull's primary purpose was to forbid other Christian nations from infringing the King of Portugal's rights of trade and colonisation in these regions, particularly amid the Portuguese and Castilian competition for ascendancy over new lands discovered.This bull should not be confused with a 21 September 1451 bull by the same name, also written by Nicholas V, relieving the dukes of Austria from any potential ecclesiastical censure for permitting Jews to dwell there.

A papal bull is a type of public decree, letters patent, or charter issued by a pope of the Catholic Church. It is named after the leaden seal (bulla) that was traditionally appended to the end in order to authenticate it.