Peter B. Lewis, the Princeton University alumnus who became its most generous donor in the modern era, died suddenly Saturday at his home in Coconut Grove, Florida, of an apparent heart attack. Mr. Lewis, who was 80, graduated from Princeton in 1955.

“This is a terrible shock. It’s completely unexpected,” said former University president Shirley M. Tilghman, on Monday evening. Ms. Tilghman was preparing to leave the next morning to fly to Cleveland, Mr. Lewis’ hometown, for his funeral.

During Ms. Tilghman’s tenure as president, Mr. Lewis donated $60 million to establish the Lewis Library, designed by architect Frank Gehry, and then provided $35 million to endow the Lewis-Sigler Institute for Integrative Genomics, which Ms. Tilghman founded. But his biggest bequest was made in 2006, for $101 million С the largest single gift to Princeton on record С to endow the Lewis Center for the Arts. The complex, designed by architect Steven Holl, is currently under construction on the University campus.

“I think he was one of the last great patrons of universities who was prepared to say, ‘What is your highest priority and how can I help you achieve it?’” Ms. Tilghman said. Asked how involved he was in establishing the Lewis-Sigler Institute, she said, “The amount he knew about genomics could fit into a thimble with room for lots of other things. He was really driven by his desire to be as helpful as he could.”

Mr. Lewis served as a member of Princeton’s Board of Trustees from 1998 to 2003. He became an emeritus trustee this year. “He believed he received a really world-class education at Princeton, and it held him in good stead the rest of his life,” Ms. Tilghman said. “He was also grateful to the University for embracing him at a time when he was getting a lot of criticism in the press about his support for legalized marijuana, and his lifestyle that he never pretended was anything other than what it was. He was, let’s say, a free spirit.”

It was after having his leg amputated and using marijuana as a pain medication that Mr. Lewis became passionate about its legalization. He gave generously to drug reform initiatives, spending over $40 million since the 1980’s, according to Forbes Magazine.

Mr. Lewis was born November 11, 1933, in Cleveland. He graduated from Princeton’s Woodrow Wilson School of Public and International Affairs. He then went to work in Cleveland at Progressive Corporation, a company his father founded that specialized in providing insurance to risky drivers. Mr. Lewis acquired control of the 100-employee company in 1965 and led it through a major expansion. Today, it is the fourth largest auto insurer in the United States and has 26,000 employees with annual sales of $17 billion.

Mr. Lewis’s funding of the Lewis-Sigler Institute was made in honor of his classmate and roommate, the late Paul Sigler. “They were roommates and remained lifelong friends,” said Ms. Tilghman. “Paul was very important in reassuring Peter that supporting this genomics institute was a good decision. He was a biophysicist and knew very well what we were trying to do. Peter joined their names together in the Institute as a gesture of their great friendship.”

Mr. Lewis was a patron of the arts, but his passion was visual rather than performing arts. “Had it been possible for us to think that our highest priority was to build a museum, he would have happily given us a gift for that,” Ms. Tilghman said. “But it wasn’t our highest priority. When I described to him why I felt so strongly about the performing arts center, he barely blinked.”

Mr. Lewis is survived by his wife, Janet Rosel Lewis; his brother Daniel Lewis; children Ivy, Jonathan, and Adam; and five grandchildren as well as his ex-wife, Toby Devan Lewis.

Said current University president Christopher L. Eisgruber, “Peter Lewis’ contributions to Princeton are legendary. He was not only a benefactor but also a visionary who pushed us — and enabled us — to aim at ever higher levels of excellence.”