His publisher Geoff Kloske of Riverhead Books said Matthiessen, who had been diagnosed with leukemia, was ill "for some months." He died at a hospital near his home on Long Island.
"Peter was a force of nature, relentlessly curious, persistent, demanding - of himself and others," his literary agent, Neil Olson, said in a statement. "But he was also funny, deeply wise and compassionate."
Few authors could claim such a wide range of achievements. Matthiessen helped found The Paris Review, one of the most influential literary magazines, and won National Book Awards for The Snow Leopard, his spiritual account of the Himalayas, and for the novel Shadow Country.
A leading environmentalist and wilderness writer, he embraced the best and worst that nature could bring him, whether trekking across the Himalayas, parrying sharks in Australia or enduring a hurricane in Antarctica.
He also was a longtime liberal who befriended Cesar Chavez and wrote a defense of Indian activist Leonard Peltier, In the Spirit of Crazy Horse, that led to a highly publicized, and unsuccessful, lawsuit by an FBI agent who claimed Matthiessen had defamed him.
Latest Book Being Published Next WeekIn Paradise, which he had expected to be his last novel, will be published next week. The book was inspired by a visit in the 1990s he made to Auschwitz.
"The gas chambers were all blown up at the end of the war, so they are simply these grim-looking pale ruins out in the distance," he told NPR during a recent interview. "It's a very grim scene. And so it's the enormity of it that just stuns you the first time."
Matthiessen became a Zen Buddhist in the 1960s, and was later a Zen priest who met daily with a fellow group of practitioners in a meditation hut that he converted from an old stable. The granite-faced author, rugged and athletic into his 80s, seemed to live out a modern version of the Buddhist legend, a child of privilege transformed by the discovery of suffering.
Matthiessen was born in New York in 1927, the son of Erard A. Matthiessen, a wealthy architect and conservationist. "The Depression had no serious effect on our well-insulated family," the author would later write.
While at Yale, he wrote the short story "Sadie," which appeared in the Atlantic Monthly, and he soon acquired an agent. After graduation he moved to Paris and, along with fellow writer-adventurer George Plimpton, helped found The Paris Review. (Matthiessen would later acknowledge he was a CIA recruit at the time and used his work with the Review as a cover).
The magazine caught on, but Paris only reminded Matthiessen that he was an American writer. In the mid-1950s he returned to the United States, moved to Long Island's Sag Harbor (where he eventually lived on a six-acre estate), socialized with Jackson Pollock, Willem de Kooning and other painters, operated a deep-sea fishing charter boat – and wrote.
Matthiessen's early novels were short, tentative efforts: Race Rock, 'Raditzer and Partisans, which features a wealthy young man who confides "his ignorance of human misery." In need of money, Matthiessen also wrote for such magazines as Holiday and Sports Illustrated.
Major Novelist Since 1961In 1961, Matthiessen became a major novelist with At Play in the Fields of the Lord, his tale of missionaries under siege from both natives and mercenaries in the jungles of Brazil. Its detailed account of a man's hallucinations brought him a letter of praise from LSD guru Timothy Leary. The book was later adapted into a film of the same name, starring John Lithgow and Daryl Hannah.
He wrote many other books, including Far Tortuga, a novel told largely in dialect about a doomed crew of sailors on the Caribbean; The Tree Where Man Was Born, a highly regarded chronicle of his travels in East Africa.
In the 1980s and '90s, Matthiessen published a trio of novels – Killing Mr. Watson, Lost Man's River and Bone by Bone – about a community in Florida's Everglades at the turn of the 20th century and a predatory planter.
Unhappy, especially with Lost Man's River, he spent years revising and condensing all three books into Shadow Country, published in 2008 and a surprise National Book Award winner.
Although an explorer in the Hemingway tradition, Matthiessen didn't seek to conquer nature, but to preserve it. In 1959, he published his first nonfiction book, Wildlife in America, in which he labels man "the highest predator" and one uniquely prone to self-destruction.
Much of his fiction, from At Play in the Fields of the Lord to Bone by Bone, bestowed a lion-like aura upon nature – grand when respected, dangerous when provoked, tragic when exploited.
"There's an elegiac quality in watching [American wilderness] go, because it's our own myth, the American frontier, that's deteriorating before our eyes," he once wrote. "I feel a deep sorrow that my kids will never get to see what I've seen, and their kids will see nothing; there's a deep sadness whenever I look at nature now."
Matthiessen was married three times, most recently to Maria Eckhart, whom he wed in 1980. He had four children, two each from his first two marriages, and two stepchildren from his third marriage.