The man from northeastern France, an online subscriber to Euromillions, hit the jackpot on December 2, but he had stopped routinely checking his numbers.
Winners have two months to present their tickets.
"It's a story with a happy ending," the man told Francaise des Jeux, who run the lottery in France. "To think that for more than a month I didn't realise I was carrying around a lottery ticket worth USD 84 million in my wallet every day!"