Antipope Eulalius (died 423) was an antipope who reigned from December 418 to April 419, although elected the day before Pope Boniface I.

Honorius, the Emperor, called a Synod — the first intervention by the Emperor in a Papal election — to decide upon the matter. There being no clear result he ordered both claimants out of Rome prior to a second synod. Eulalius, however, remained, until expelled following clashes involving his supporters.

When the second synod decided in favour of Boniface, Eulalius accepted the result, subsequently becoming a bishop under Celestine I and dying in 423.

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