Joliet, Jolliet, Louis (1645–1700), a French-Canadian explorer. In 1673 Joliet and Father Jacques Marquette explored the Mississippi River, traveling 2,500 miles (4,000 km) by canoe. They discovered two river-and-portage routes linking Lake Michigan with the Mississippi, and were probably the first Europeans to see the upper reaches of that river.

Joliet was born at Beaupré, Quebec. After attending a Jesuit seminary he received further schooling in France. Returning to New France in 1668, he engaged in the fur trade and explored the Great Lakes region. In 1672 Joliet was chosen by Governor Frontenac to explore the Mississippi and determine whether it flowed into the Pacific Ocean. (The river had been discovered in 1541 by DeSoto, but very little was known of its course.) Joliet took six companions, including Father Marquette, the chaplain.

Starting from St. Ignace, Michigan, the party paddled down Lake Michigan, entered the Fox River at its mouth in Green Bay, crossed the short portage to the Wisconsin River, and from there entered the Mississippi. After nearing the mouth of the Arkansas River they turned back, as Joliet was convinced the Mississippi entered the Gulf of Mexico and feared capture by the Spanish or by hostile Indians. On the return trip, the party paddled up the Illinois River and crossed the Chicago portage to Lake Michigan.

Joliet lost his journal in the St. Lawrence rapids, but redrew his maps from memory. He later explored the Labrador coast and Hudson Bay.