Puzo died, apparently of heart failure, at his Long Island home, said Neil Olson, his literary agent. Puzo had just finished work on his latest book, Omerta. The book is due out in July 2000.
Puzo, who wrote seven other novels in addition to The Godfather, was born in New York, the son of illiterate Italian immigrants. After serving in World War II, he began his writing career starting out doing pulp stories for men's magazines.
But his literary ambitions were much higher, and he published his first novel, The Dark Arena, in 1955.
Puzo's next book was an autobiographical piece about the Italian immigrant experience, but it failed to reach many readers. The following book covered a different immigrant experience: It focused on the Corleone family, Italians who came to the United States and plunged into the world of organized crime.
It was called The Godfather. The book sold more than 21 million copies worldwide, and spawned three movies that became American cinematic classics. Marlon Brando, Al Pacino and Robert De Niro brought Puzo's characters to the screen; Puzo co-wrote the screenplays with director Francis Ford Coppola.
He co-wrote several other screenplays, including two Superman movies, as well as The Cotton Club and Christopher Columbus.
In 1984, he brought out another best-seller, The Sicilian.
Puzo's other books included Fool's Diet, a 1978 effort on casinos; 1992's The Fourth K, a futuristic political thriller; and The Last Don in 1996, a return to his favorite topic, the Mafia.
The Last Don became another runaway bestseller and was the basis for a highly rated television miniseries.
He insisted that his research was done in libraries, not amid gangsters, denying he had any vague links to organized crime.
"Where would I have time to be in the Mafia?" he asked in a 1996 Associated Press interview. "I starved before the success of The Godfather. If I was in the Mafia I would have made enough money so I wouldn't have to write."
He acknowledged his portrayals, with their emphasis on honor and family, made the Mafia a more romantic place than the thuggery or buffoonery of the real thing.
"They're not my Mafia," he said of the real-life mobsters. "My Mafia is a very romanticized myth."
And anyway, he asked, "Just because a guy's a murderer, he can't have endearing traits?"
Puzo spent the last three years working on Omerta, a book about a mob family on the brink of legitimacy. Omerta is the mob code of silence.
"It's vintage Puzo," said his editor, Jonathan Karp, who recently read the completed book. "He was a virtuoso toryteller right up to the end."
Puzo is survived by his children, Anthony, Dorothy, Eugene, Virginia and Joseph; a sister, Evelyn Murphy, a brother, Anthony Cleri; his companion of 20 years, Carol Gino; and nine grandchildren.
His wife, Erika, died in 1978.
A private family service is planned for Monday, Olson said.