Radisson was born in France and emigrated to Canada in 1651 with his family. Within months, while out walking with friends he was captured by the Iroquois (one source says the Mohawks), who killed the other boys, and he was adopted by a family which had lost three sons in wars (the couple also had a surviving son and two daughters), who named him Oninga.
As a captive he settled quickly and happily into his new life, learning the Iroquois language, and apparently did not take advantage of several opportunities to escape. But in 1653 he did escape and rejoin white society, becoming an explorer and fur trader.
With his brother-in-law, Médard Chouart, Sieur des Groseilliers, he was the first European to explore Lake Superior, making good use of the survival skills he had learned from the Iroquois. They returned to European civilization with a very large cargo of furs, which were confiscated in Montréal by the government because they had been obtained without a license. This turned both men against the French government and they went to England, where they influenced the founding of the Hudson's Bay Company in 1670, who employed them as guides and advisors.
Radisson founded Port Nelson, the first permanent European settlement in Manitoba. After retiring he settled in England in 1687.