Henri de Tonti was probably born near Gaeta, Italy in either 1649 or 1650. He was the son of Lorenzo de Tonti who was a financier and former governor of Gaeta. Lorenzo de Tonti was the inventor of the form of life insurance known as the tontine.
Lorenzo was involved in a revolt against the Spanish viceroy in Naples, Italy and was forced to seek political asylum in France around the time of Henri's birth.
In 1668 Henri joined the French Army and later served in the French Navy. During the Sicilian Wars Henri lost his hand in a grenade explosion and from that time on wore a prosthetic hook covered by a glove thus earning the nickname "Iron Hand".
In the summer of 1678 Tonti journeyed with the famous René Robert Cavelier, Sieur de La Salle who recognized him as an able associate. La Salle left Tonti to hold Fort Crèvecoeur in Illinois while La Salle returned to Ontario.
In the spring of 1682 Tonti journeyed with La Salle on his famous descent of the Mississippi River. Tonti's letters and journals are valuable source materials on these explorations.
When La Salle returned to France in 1683 he left Tonti behind to hold Fort Saint Louis on the Illinois River. Three years later he learned that La Salle was returning to ascend the Mississippi from the Gulf of Mexico and proceeded south on his own to try and meet La Salle on his ascent. He failed to find La Salle and made it to the Gulf of Mexico before turning back. He left several men at the mouth of the Arkansas River to establish a trading post which would later become the historical town of Arkansas Post, Arkansas.
During 1687 Tonti was engaged in wars with the English and their Iroquois allies. In 1688 he returned to Fort Saint Louis and found members of La Salle's party who concealed the fact of La Salle's death. Tonti sent out parties to find survivors and then started out himself in October of 1869.
Tonti travelled up the Red River and reached the Caddo villages in northeastern Texas in the spring on 1690. The Caddo offered him no assistance and he was forced to withdraw.
Tonti experienced several financial difficulties in the 1690s and in early 1700 Tonti commenced a journey down the Mississippi to make contact with Pierre Le Moyne d'Iberville who had established the Louisiana colony. Tonti reached Louisiana and joined the colony. In 1702 he was chosen as an ambassador to the Choctaw and Chickasaw tribes and conducted several negotiations as well as leading punitive expeditions until 1704.
In August of 1704 Tonti contracted yellow fever and died at Old Mobile near present day Mobile, Alabama.