Louis Hennepin, a Franciscan (Recollect) missionary and explorer of the Mississippi river, born at Ath, Belgium, about 1640, died in Holland subsequent to 1701. After his entrance into the Franciscan order, he made a tour through Germany and Italy, at the close of which he was settled for a year as preacher at Halles in Belgium. His superiors then sent him to Artois, whence he journeyed to Holland, and for eight months had charge of a hospital at Maestricht. At the battle of Senef, between the prince of Conde and William of Orange, in 1674, ho was present as regimental chaplain. The next year he was ordered to Canada, and embarked in company with Bishop Laval, whose favor he managed to secure on the voyage, and with the sieur de la Salle. He preached for a while at Quebec. In 1676 he went to the Indian mission at Fort Frontenac, whence he visited the Mohawk country. In 1678 he was attached to La Salle's expedition, and accompanied the chevalier de Tonty and the sieur de la Motte from Fort Frontenac to Niagara, where La Salle constructed the Griffin, a vessel for navigating the lakes above the falls. This accomplished, La Salle on Aug. 7, 1679, began his voyage.

He passed through Lakes Erie, Huron, and Michigan, to the mouth of the St. Joseph's river, ascended this in canoes to the portage, carried them five or six miles to the Kankakee, and floated down this stream and the Iroquois to the Illinois, on which they built Fort Crevecoeur, a little below the present site of Peoria. Hearing no tidings of the Griffin, which he had sent back, La Salle returned to Fort Frontenac for supplies, charging Michel Acau, Father Hennepin, and one other with a voyage of discovery, the precise object of which is unknown, but making the mouth of the Wisconsin a rendezvous. Hennepin set out in a canoe, Feb. 29, 1680, and followed the Illinois to its mouth. The party then explored the Mississippi till April 11, when they were taken by a party of Sioux and carried up the river to their villages. During this time Hennepin discovered and named the falls of St. Anthony. Daniel Greysolon du Luht had penetrated to the Sioux country by way of Lake Superior, and made peace with the tribe.

Hearing that three Frenchmen were held prisoners, he advanced to where they were, and rescued them in July. He took them down the Mississippi to the Wisconsin, and passed up that river and down the Fox, and so through Green bay to Lake Michigan. From Quebec Hennepin sailed for France, where he published in 1683 his Description de la Louisiane, nouvelle-ment decouverte au sud-ouest de la Nouvelle France, etc. (12mo, Paris), containing the fullest published account of La Salle's first expedition, and of Hennepin's own explorations, with a description of the upper Mississippi. Notwithstanding the writer's vanity and fondness for exaggeration, this work is valuable. Hennepin was now appointed guardian of a convent at Renti in Artois; but refusing to return to America in obedience to his ecclesiastical superiors, he was compelled to leave France, and proceeding to Holland in lay dress sought the favor of William III. of England. In 1697, 10 years after La Salle's death, Hennepin published his extraordinary Nouvelle decouverte d'un tres grand pays situe dans l'Amerique entre le Nouveau Mexiqve et la Mer Glaciale, etc. (12mo, Utrecht). In this work, which embodies his Description de la Louisiane, written anew and enlarged, he asserts that he descended to the mouth of the Mississippi, and was the first European who floated on that river.

He gives a journal, description of the scenery, Indian tribes, and the distances along the route, identical with that of Pere Membre published by Le Clercq. Hennepin explained his long silence on this important point by saying that he feared the enmity of La Salle, who had ordered him to follow a different course, and who prided himself upon being the first who descended the Mississippi to the gulf of Mexico. Notwithstanding the utter impossibility of reconciling the dates given in Hennepin's narrative, the story obtained general credence until its falseness was exposed by Jared Sparks. (See "Life of La Salle," by Sparks, in the " Library of American Biography.") His third work, published at Utrecht in 1698, Nouveau voyage dans un pays plus grand que l'Europe, was a compilation describing La Salle's voyage to the month of the Mississippi. Of these three works at least 24 editions appeared in various languages. He endeavored to return to Canada in 1699, but Louis XIV. ordered his arrest if he arrived there.

He is said to have been at Rome in 1701, seeking to establish a mission on the Mississippi.