Cassien de Nantes was a 17th-century French Capuchin missionary priest born in Nantes to parents of Portuguese descent. Alongside his companion, Agathange of Vendome, he traveled extensively through Syria and Egypt before reaching Ethiopia. During his mission in Africa, he was accused of preaching to the Coptic community. This led to his execution by the King of Gondar, who ordered that he be killed by a blow to the head.