Franciscan missionary who, with the celebrated explorer René Robert Cavelier, Sieur de La Salle (La Salle, René-Robert Cavelier, sieur (lord) de), penetrated the Great Lakes in 1679 to the region of Illinois and wrote the first published description of the country.

Hennepin joined the Récollet Order of Friars Minor, Béthune, France, and in 1675 went to Canada with La Salle, whose chaplain he became in 1678. Together they reached the site of Peoria, Ill. (January 1680), where they established Fort-Crèvecoeur. La Salle then returned to Fort Frontenac (at Kingston, Ont.) for supplies, while Hennepin and the remainder of the party explored the upper Mississippi River. In April they were captured by Sioux Indians, whom they accompanied on several hunting expeditions, during the course of which they reached what Hennepin named the Falls of St. Anthony (site of Minneapolis, Minn.). Hennepin was rescued by the French voyageur Daniel Greysolon, Sieur Dulhut, in July 1680. Returning to France in 1682, he wrote a full account of his exploits, Description de la Louisiane (1683), later revised as Nouvelle découverte d'un très grand pays situé dans l'Amérique (1697; “New Discovery of a Very Large Country Situated in America”), in which he claimed to have explored the Mississippi to its mouth. This bold assumption was, however, soon discredited. Hennepin spent his final years in obscurity, being last heard of in a Roman monastery in 1701.