A Protopope, or Protopresbyter, is a priest of higher rank in the Orthodox and Byzantine Catholic Churches, corresponding in general to the Western archpriest or Latin dean.
The rights and duties of these dignitaries have varied to some extent at different times and in different local Churches. Roughly, the titles archpriest (in Greek ἀρχιπρεσβὐτερος archipresbyteros), protoiereus (πρωτοιερεύς protoiereus, πρωτοπρεσβύτερος protopresbyteros), protopope may be taken as meaning the same thing, though they have occasionally been distinguished.
The general idea is that the archpriest has the highest rank in his order; he comes immediately after the bishop. In the fifth century he appears as head of the college of priests, as the bishop's delegate for certain duties of visitation and canonical judgment, as his representative in case of absence or death (sede vacante). He therefore combined the offices of the Roman Catholic dean of the chapter, vicar-general and vicar capitular. The title recurs constantly in the Early Middle Ages.
At imperial Constantinople there was an elaborately organized court of ecclesiastical persons around the Ecumenical Patriarch, whose various places in choir when the patriarch celebrated are given in the Euchologion together with a statement of their duties. Among these the protopope had the first place on the left. "The protopope stands above the left choir when the pontiff celebrates, he gives to him [the pontiff] Holy Communion and in the same way the pontiff to the protopope and he has all first places [τὰ πρωτεῖα πάντα -ta proteia panta] in the church" (Goar, 225). Under him the "second one" (ὁ δευτερεύων ho deutereuon), takes his place in his absence (ibid.). So also Leo Allatius's list, where it is said further that: "he holds the place [κρατῶν τόπον - kraton topon, as deputy] of the pontiff" (ibid., 229). He is promoted by presentation to the patriarch, who lays his hand on him with prayer, and the clergy cry "axios" (ἄξιος) three times (the rite from Allatius is given by Goar, 238). Goar notes that the protopope, at least to some extent, succeeded to the place of the chorepiscopus. He could ordain lectors; at concelebrations where no bishop is present he presided and said the ekphonesis (ἐκφώνησις - exclamations chanted aloud at the end of prayers and litanies). In the bishop's absence he took his place as president, and had jurisdiction over his fellow-clergy. George Kodinos (fourteenth century) says of the protopope: "he is first in the tribunal [τοῦ βήματος - tou bematos, in authority] holding the second place after the pontiff" (De Officiis, I, quoted by Goar 237).