Clement VIII, born Gil Sánchez Muñoz y Carbón (1369/70 – 28 December 1445/46), was one of the antipopes of the Avignon obedience, reigning from 10 June 1423 to 26 July 1429.

When King Alfonso V of Aragon reached an agreement with Pope Martin V, Sánchez Muñoz abdicated, made his submission and was appointed bishop of Mallorca.

Alfonso wished to negotiate for Naples, and so gave Clement support; his queen Maria of Castile, and the Aragonese bishops supported Martin V. In the summer of 1423 Alfonso persuaded the Republic of Siena to acknowledge Clement VIII, thus securing recognition for the pope of the Avignon line in the very city, Pavia, which was part of the Republic of Siena,[dubious – discuss] where the Roman pope Martin V had convened an ecumenical council of the Church.

[citation needed] However, through the exertions of Cardinal Pierre de Foix, an able diplomat and relation of the King’s, an agreement was reached between Alfonso and the Pope.

Clement declared his abdication on 26 July 1429 and had his cardinals elect Oddone Colonna (Martin V) his successor, a formal act precluding future doubts concerning apostolic succession.