Peter Matthiessen was an American novelist, naturalist, wilderness writer, Zen teacher, and onetime CIA agent. He was a co-founder of the literary magazine The Paris Review and remains the only writer to have won the National Book Award in both nonfiction for The Snow Leopard (1979) and fiction for Shadow Country (2008). Matthiessen was also a prominent environmental activist.

His nonfiction work featured nature and travel, notably The Snow Leopard (1978), and American Indian issues and history, such as his detailed and controversial study of the Leonard Peltier case, In the Spirit of Crazy Horse (1983). His fiction was adapted for film: the early story "Travelin' Man" was made into The Young One (1960) by Luis Buñuel and the novel At Play in the Fields of the Lord (1965) became the 1991 film of the same name.

In 2008, at age 81, Matthiessen received the National Book Award for Fiction for Shadow Country, a one-volume, 890-page revision of his three novels set in frontier Florida published in the 1990s. Critic Michael Dirda once noted, "No one writes more lyrically [than Matthiessen] about animals or describes more movingly the spiritual experience of mountaintops, savannas, and the sea."

He was treated for acute leukemia for more than a year and died on April 5, 2014, just three days before the publication of his final book, the novel In Paradise on April 8.