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Shortest-reigning popes

There have been a number of popes whose reign lasted about a month or less. In the following list the number of calendar days includes partial days. Thus, for example, if a pope's reign commenced on 1 August and he died on 2 August, this counts as reigning for two calendar days.

Stephen (23–26 March 752) died of stroke three days after his election, and before his consecration as a bishop. He is not recognized as a valid pope, but was added to the lists of popes in the 15th century as Stephen II, causing difficulties in enumerating later popes named Stephen. The Holy See's Annuario Pontificio, in its list of popes and antipopes, attaches a footnote to its mention of Pope Stephen II:

On the death of Zachary the Roman priest Stephen was elected; but, since four days later he died, before his consecratio, which according to the canon law of the time was the true commencement of his pontificate, his name is not registered in the Liber Pontificalis nor in other lists of the popes.

Published every year by the Roman Curia, the Annuario Pontificio attaches no consecutive numbers to the popes, stating that it is impossible to decide which side represented at various times the legitimate succession, in particular regarding Pope Leo VIII, Pope Benedict V and some mid-11th-century popes.