(antipope 5 Nov. 1439–7 Apr. 1449: d. 7 Jan. 1451)
After deposing Eugene IV the council of Basle (1431–49) elected Amadeus VIII, duke of Savoy, in his place. The election was irregular, being carried out by one cardinal and 32 electors nominated by a commission, but it demonstrated the council's resolve to choose someone of wealth and international standing as well as holiness. Born at Chambéry on 4 Dec. 1383, Amadeus succeeded his father Count Amadeus VII in 1391, and by astute diplomacy so extended his realm that it eventually included Piedmont and stretched from Neuchâtel in the north to the Ligurian coast. In recognition of his power Sigismund, German king and later emperor (1433–7), raised Savoy to a duchy in 1416. In Oct. 1434, deeply affected by the deaths of his wife (1422) and eldest son (1431), he withdrew to the chateau of Ripaille, near Thonon on the Lake of Geneva, where he founded and governed an order of knights-hermits of St Maurice. He planned to keep the diplomatic business of Savoy in his own hands, while leaving day-to-day administration to his second son Ludovico.
A profoundly spiritual layman, he accepted his election only with great hesitation on 14 Dec. 1439, abdicating as duke on 6 Jan. 1440 and, after ordination and consecration, being crowned as Felix V at Basle on 24 June. He failed to secure recognition, however, beyond his own territories and a few smaller states; the greater powers held aloof or were hostile. He nominated several eminent men as cardinals, although some declined his invitation; for a time he employed Enea Silvio Piccolomini (later Pius II) as his secretary. But his relations with the rump council, which should have been his chief support, were never happy; on 17 Nov. 1442, wearied by the fathers' studied insults, he retired to Lausanne and then Geneva. By 1445 he was beginning to look for release from an impasse as embarrassing to himself as it was becoming dangerous to his family. In 1449, through the mediation of Charles VII of France (1422–61), an accommodation was at last reached with the new Roman pope, Nicholas V, as a result of which Felix solemnly abdicated on 7 Apr., having first retracted all the censures pronounced on his adversaries. In return Nicholas appointed him (18 June) cardinal bishop of Sta Sabina, with a substantial pension, and also papal vicar and legate in Savoy and adjacent dioceses. The last of the antipopes, he did not long enjoy these dignities but died at Geneva on 7 Jan. 1451; he was buried at Ripaille.
His Bullarium (8 vols., unprinted) is in the Archivio di Stato of Turin.F. Cognasso, Amadeo VIII (Turin, 1930)DBI ii. 749–53 (F. Cognasso)DHGE ii. 1166–74 (G. Mollat)EC v. 1136 f. (G. B. Picotti)EThC 37–8 (H. Müller)Histoire vi. 130–31 (P. Ourliac)Levillain i. 574 (E. Mongiano)MC iiSeppelt iv. 295 f., 299 f., 302 f.