Little is known of François in his early years beyond his birth in Château de Fénelon in Périgord until he left for the missions of New France in 1667 as yet not an ordained priest.
He and M. Claude Trouvé left almost immediately to establish a mission for the Iroquois, at their request, near the Bay of Quinte on Lake Ontario.
(A letter by Trouvé is appended to François Dollier de Casson's Histoire du Montréal and gives a good summary of the Kenté (Quinté) mission).
Fénelon spent the winter of 1669–1670 at Ganatsekwyagon, an Iroquoian village at the mouth of the Rouge River and resulted in the nearby Frenchman's Bay being named for him.
[2] In 1672 he was recalled from Kenté to establish an Algonquin mission on the outskirts of Ville-Marie at a place called Gentilly.