For current procedures regarding the election of the pope, see Pope John Paul II's 1996 Apostolic Constitution UNIVERSI DOMINICI GREGIS. See also PAPAL ELECTIONS and CONCLAVE.

The supreme headship of the Church is, we have seen, annexed to the office of Roman bishop. The pope becomes chief pastor because he is Bishop of Rome: he does not become Bishop of Rome because he has been chosen to be head of the universal Church. Thus, an election to the papacy is, properly speaking, primarily an election to the local bishopric. The right to elect their bishop has ever belonged to the members of the Roman Church. They possess the prerogative of giving to the universal Church her chief pastor; they do not receive their bishop in virtue of his election by the universal Church. This is not to say that the election should be by popular vote of the Romans. In ecclesiastical affairs it is always for the hierarchy to guide the decisions of the flock. The choice of a bishop belongs to the clergy: it may be confined to the leading members of the clergy. It is so in the Roman Church at present. The electoral college of cardinals exercise their office because they are the chief of the Roman clergy. Should the college of cardinals ever become extinct, the duty of choosing a supreme pastor would fall, not on the bishops assembled in council, but upon the remaining Roman clergy. At the time of the Council of Trent Pius IV, thinking it possible that in the event of his death the council might lay some claim to the right, insisted on this point in a consistorial allocution.

It is thus plain that a pope cannot nominate his successor. History tells us of one pope – Benedict II (530) – who meditated adopting this course. But he recognized that it would be a false step, and burnt the document which he had drawn up for the purpose. On the other hand the Church's canon law (10 D. 79) supposes that the pope may make provision for the needs of the Church by suggesting to the cardinals some one whom he regards as fitted for the office: and we know that Gregory VII secured in this way the election of Victor III. Such a step, however, does not in any way fetter the action of the cardinals. The pope can, further, legislate regarding the mode in which the subsequent election shall be carried out, determining the composition of the electoral college, and the conditions requisite for a definitive choice. The method at present followed is the result of a series of enactments on this subject.

A brief historical review will show how the principle of election by the Roman Church has been maintained through all the vicissitudes of papal elections. St. Cyprian tells us in regard to the election of Pope St. Cornelius (251) that the comprovincial bishops, the clergy, and the people all took part in it: "He was made bishop by the decree of God and of His Church, by the testimony of nearly all the clergy, by the college of aged bishops [sacerdotum], and of good men"(Ep. Iv ad Anton., n. 8). And a precisely similar ground is alleged by the Roman priests in their letter to Emperor Honorius regarding the validity of the election of Boniface I (A.D. 418; P.L., XX, 750). Previous to the fall of the Western Empire interference by the civil power seems to have been inconsiderable. Constantius, it is true, endeavoured to set up an antipope, Felix II (355), but the act was universally regarded as heretical. Honorius on the occasion of the contested election of 418 decreed that, when the election was dubious, neither party should hold the papacy, but that a new election should take place. This method was applied at the elections of Conon (686) and Sergius I (687). The law is found in the Church's code (c. 8, d. LXXIX), though Gratian declares it void of force as having emanated from civil and not ecclesiastical authority (d. XCVI, proem.; d. XCVII, proem.). After the barbarian conquest of Italy, the Church's rights were less carefully observed. Basilius, the prefect of Odoacer, claimed the right of supervising the election of 483 in the name of his master, alleging that Pope Simplicius had himself requested him to do so (Hard., II, 977). The disturbances which occurred at the disputed election of Symmachus (498) led that pope to hold a council and to decree the severest penalties on all who should be guilty of canvassing or bribery in order to attain the pontificate. It was moreover decided that the majority of votes should decide the election. Theodoric the Ostrogoth, who at this period ruled Italy, became in his later years a persecutor of the Church. He even went so far as to appoint Felix III (IV) in 526 as the successor of Pope John I, whose death was due to the incarceration to which the king had condemned him. Felix, however, was personally worthy of the office, and the appointment was confirmed by a subsequent election. The precedent of interference set by Theodoric was fruitful of evil to the Church. After the destruction of the Gothic monarchy (537), the Byzantine emperors went even farther than the heretical Ostrogoth in encroaching on ecclesiastical rights. Vigilius (540) and Pelagius I (553) were forced on the Church at imperial dictation. In the case of the latter there seems to have been no election: his title was validated solely through his recognition as bishop by clergy and people. The formalities of election at this time were as follows (Lib. Diurnus Rom. Pont., 2, in P.L., CV, 27). After the pope's death, the archpriest, the archdeacon and the primicerius of the notaries sent an official notification to the exarch at Ravenna. On the third day after the decease the new pope was elected, being invariably chosen from among the presbyters or deacons of the Roman Church (cf. op. cit., 2, titt. 2, 3 5), and an embassy was despatched to Constantinople to request the official confirmation of the election. Not until this had been received did the consecration take place. The Church acquired greater freedom after the Lombard invasion of 568 had destroyed the prestige of Byzantine power in Italy. Pelagius II (,578) and Gregory I (590) were the spontaneous choice of the electors. And in 684, owing to the long delays involved in the journey to Constantinople, Constantine IV (Pogonatus) acceded to Benedict II's request that in future it should not be necessary to wait for confirmation, but that a mere notification of the election would suffice. The 1088 of the exarchate and the iconoclastic heresy of the Byzantine court completed the severance between Rome and the Eastern Empire, and Pope Zacharias (741) dispensed altogether with the customary notice to Constantinople.

In 769 a council was held under Stephen III to rectify the confusion caused by the intrusion of the antipope Constantine. This usurper was a layman hurriedly raised to priest's orders to render his nomination to the pontificate possible. To make a repetition of the scandal impossible it was decreed that only members of the sacred college were eligible for election. The part of the laity was, moreover, reduced to a mere right of acclamation. Under Charlemagne and Louis the Pious the Church retained her freedom. Lothair, however, claimed more ample rights for the civil power. In 824 he exacted an oath from the Romans that none should be consecrated pope without the permission and the presence of his ambassadors. This was, in fact, done at most of the elections during the ninth century, and in 898 the riots which ensued upon the death of Pope Stephen V led John IX to give ecclesiastical sanction to this system of imperial control. In a council held at Rome in that year he decreed that the election should be made by bishops (cardinal) and clergy, regard being had to the wishes of the people, but that no consecration should take place except in the presence of the imperial legate (Mansi XVIII, 225).

The due formalities at least of election appear to have been observed through the wild disorders which followed the collapse of the Carlovingian Empire: and the same is true as regards the times of Otto the Great and his son. Under the restored empire, however, the electors enjoyed no freedom of choice. Otto I even compelled the Romans to swear that they would never elect or ordain a pope without his or his son's consent (963; cf. Liutprand, "Hist. Ott.", viii). In 1046 the scandals of the preceding elections, in which the supreme pontificate had become a prize for rival factions entirely regardless of what means they employed, led clergy and people to leave the nomination to Henry III. Three popes were chosen in this manner. But Leo IX insisted that the Church was free in the choice of her pastors, and, until he was duly elected at Rome, declined to assume any of the state of his office. The party of reform, of which Hildebrand was the moving spirit, were eager for some measure which should restore an independent choice to the Church. This was carried out by Nicholas II. In 1059 he held a council in the Lateran and issued the Decree "In Nomine". This document is found in two recensions, a papal and an imperial, both of early date. There is however little doubt that the papal recension embodied in the "Decretum Gratiani" (c. 1. d. XXIII) is genuine, and that the other was altered in the interest of the antipope Guibert. The right of election is confined to the cardinals, the effective choice being placed in the hands of the cardinal bishops: clergy and people have a right of acclamation only. The right of confirmation is granted to the Emperor Henry IV and to such of his successors as should personally request and receive the privilege. The pope need not necessarily be taken from the number of cardinals, though this should be the case if possible.

This decree formed the basis of the present legislation on the papal election, though the system underwent considerable development. The first important modification was the Constitution "Licet de Vitanda" [c. vi, X, "De elect." (I, 6)] of Alexander III, the first of the decrees passed by the Third Oecumenical Council of the Lateran (1179). To prevent the evils of a disputed election it was established by this law that no one should be held to be elected until two thirds of the cardinals should have given their votes for him. In this decree no distinction is made between the rights of the cardinal bishops and those of the rest of the Sacred College. The imperial privilege of confirming the election had already become obsolete owing to the breach between the Church and the Empire under Henry IV and Frederick I. Between the death of Clement IV (1268) and the coronation of Gregory X (1272) an interregnum of nearly three years intervened. To prevent a repetition of so great a misfortune the pope in the Council of Lyons (1179) issued the Decree "Ubi periculum" [c. iii, "De elect.", in 60 (I, 6)], by which it was ordained that during the election of a pontiff the cardinals should be secluded from the world under exceedingly stringent regulations, and that the seclusion should continue till they had fulfilled their duty of providing the Church with a supreme pastor. To this electoral session was given the name of the Conclave. This system prevails at the present day.