The donor whose $350 million gift will be critical in building Cornell University’s new high-tech graduate school on Roosevelt Island is Atlantic Philanthropies, whose founder, Charles F. Feeney, is a Cornell alumnus who made billions of dollars through the Duty Free Shoppers Group.

Mr. Feeney, 80, has spent much of the last three decades giving away his fortune, with large gifts to universities all over the world and an unusual degree of anonymity. Cornell officials revealed in 2007 that he had given some $600 million to the university over the years, yet nothing on its Ithaca campus — where he graduated from the School of Hotel Management in 1956 — bears Mr. Feeney’s name.

The $350 million gift, the largest in the university’s history, was announced on Friday, but the donor was not named. Officials at Atlantic Philanthropies confirmed on Monday evening that it was Mr. Feeney, a native of Elizabeth, N.J., who is known for his frugality — he flies coach, owns neither a home nor a car, and wears a $15 watch — as well as his philanthropic generosity, particularly to medical research.

“This is a once-in-a-generation opportunity,” Mr. Feeney said in a statement released by Atlantic Philanthropies, “to create economic and educational opportunity on a transformational scale.”

The statement echoed what Mayor Michael R. Bloomberg said hours earlier at a news conference officially crowning Cornell, with its partner, Technion-Israel Institute of Technology, the winner of an intense international competition to build the new graduate school.

“Today will be remembered as a defining moment,” Mr. Bloomberg said, making official what had been apparent since Cornell’s chief rival, Stanford University, withdrew its bid for the campus on Friday. “In a word, this project is going to be transformative.”

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