He was one of the older sons of Charles le Moyne (q. v.), and with his brothers, Serigny, Bienville (q. v.), and Chateaugay, was prominent in the early history of Louisiana.

At the age of fourteen he entered the French navy as a midshipman, and soon saw active service in the New World.

He accompanied De Troye on his overland expedition from Canada against the English forts on Hudson bay, was at the taking of Fort Monsipi, and, having captured two vessels, reduced Fort Quitchitchonen, and again in 1688-89, capturing two English vessels in that locality. In 1690 he was one of the leaders in the retaliatory expedition against Schenectady, where he saved the life of John Sanders Glen, and in Ottobet, 1694, took Fort Nelson, on Hudson bay, losing his brother Louis in the assault.

Meanwhile, in 1692, he had been given command of a frigate. While cruising in the Bay of Fundy with three vessels, he defeated three English ships, capturing the "Newport" near the mouth of the St. John's, then besieged, captured, and demolished Fort Pemaquid, and ravaged Newfoundland, taking almost all the English posts. In 1697 he went to Hudson bay with the "Pelican," and after defeating three English vessels reduced Fort Bourbon.

His reputation was now at its height, and he was regarded as the most skilful naval officer in the French service, and "the idol of his countrymen." He obtained a commission for establishing direct intercourse between France and the Mississippi, and on 17 October, 1698, left Brest with two frigates, two smaller vessels, and about two hundred settlers. After stopping at Santo Domingo and Pensacola, he reached Mobile bay, 31 January, 1699, and anchored near Massacre island, he erected huts on Ship island, and discovered the river Pascagoula and the tribes of the Biloxi.

He then went with his brother Bienville, in two barges, to seek the mouth of the Mississippi, and on 2 March entered that river, which they ascended to the village of the Bayagoulas, and probably reached the mouth of Red river.

A letter from Tonti to La Salle, written in 1686, was given to the party by the Indians, and satisfied them that they were really on the Mississippi. Returning to his ships, Iberville built old Fort Biloxi, the first post on the Mississippi, at the head of Biloxi bay, placed Sauvolle in command, and made his brother Bienville ldng's lieutenant.

In May, 1699, he sailed for France; but in January of the following year he again reached Fort Biloxi in command of the "Renominde," and soon afterward built a new fort on the Mississippi, over which he placed Bienville.

In April he sent Lesueur with a party to establish a post at the copper-mines on Mankato, and in a fort among the low as they passed a fruitless winter.

Iberville was again in Louisiana in December, 1701, and, finding the colony reduced by disease, transferred the settlement to Mobile, beginning the colonization of Alabama, and also occupying Dauphin, or Massacre island.

His health had become seriously undermined by fevers, and he was called away from his Louisiana projects by the government, having been made, in 1702, captain of a line-of-battle ship.

In 1706, with his fleet, he captured the island of Nevis, and was about to cruise off the coast of North Carolina, when he was stricken with a fatal malady and taken to Havana.