His death was confirmed by Julio Ortega, his biographer and a professor of Hispanic studies at Brown University, where Mr. Fuentes taught for several years. No cause was given.
Mr. Fuentes was one the most admired writers in the Spanish-speaking world, a catalyst, along with Gabriel García Márquez, Mario Vargas Llosa and Julio Cortazar, of the explosion of Latin American literature in the 1960s and ’70s known as “El Boom.” He wrote plays, short stories, political nonfiction and more than a dozen novels, many of them chronicles of tangled love, that were acclaimed throughout Latin America.
Mr. Fuentes received wide recognition in the United States in 1985 with his novel “The Old Gringo,” a convoluted tale of the American writer Ambrose Bierce, who disappeared during the Mexican Revolution. The first book by a Mexican novelist to become a best seller north of the border, it was made into a film starring Gregory Peck and Jane Fonda, released in 1989.
In the tradition of Latin American writers, Mr. Fuentes was an outspoken public intellectual, writing magazine, newspaper and journal articles that criticized the Mexican government during the long period of sometimes repressive single-party rule that ended in 2000 with the election of an opposition candidate, Vicente Fox Quesada. Mr. Fuentes was more ideological than political. He tended to embrace justice and basic human rights regardless of political labels. He initially supported Fidel Castro’s revolution in Cuba, but turned against it as Castro became increasingly authoritarian. He openly sympathized with Indian rebels in the southern Mexican state of Chiapas, and publicly skewered the administration of George W. Bush.
Mr. Fuentes was appointed Mexico’s ambassador to France in 1975, but he resigned two years later to protest the appointment of Gustavo Díaz Ordaz as ambassador to Spain. Mr. Díaz Ordaz had been president of Mexico in 1968 when Mexican troops opened fire on student protesters in Mexico City.
Carlos Fuentes was born on Nov. 11, 1928, in Panama, the son of Berta Macías and Rafael Fuentes, a member of Mexico’s diplomatic corps. As his father moved among Mexican embassies, Mr. Fuentes spent his early childhood in several South American countries. Then, in 1936, the family was transferred to Washington, where Mr. Fuentes learned to speak English fluently while enrolled in a public school.
In 1940 the family was transferred again, this time to Santiago, Chile, where he began to experiment with writing. In an interview with The New York Times in 1985, Mr. Fuentes said he first had to decide “whether to write in the language of my father or the language of my teachers.” He chose Spanish, he said, because he believed that it offered more flexibility than English. There was also a practical reason. English, he said, “with a long and uninterrupted literary tradition, did not need one more writer.”
He was 16 when his family finally moved back to Mexico. He knew his homeland through the stories that his grandmothers had told during the summers he spent with them.
“I think I became a writer because I heard those stories,” he said in 2006 in an interview with The Academy of Achievement, a nonprofit organization based in Washington. His grandmothers fascinated him with their tales of bandits, revolution and reckless love. “They had the whole storehouse of the past in their heads and hearts,” Mr. Fuentes said. “So this was, for me, very fascinating, this relationship with my two grannies — the two authors of my books, really.”
When he told his family that he wanted to be a writer, his father was encouraging, but insisted that he also study law, which he did in Mexico and later in Switzerland.
After completing his degree, Mr. Fuentes entered Mexico’s diplomatic service, while also carving out time for his fiction. His first novel, “Where the Air Is Clear,” was published in 1958 when he turned 30. It was a literary sensation, mixing biting social commentary with interior monologues and portrayals of the subconscious. His reputation established, Mr. Fuentes left government service to devote all his energies to writing.
He became a prolific author who said he did not spend much time rewriting and never suffered from writer’s block. He said he liked to write on the right-hand pages of lined notebooks, making changes and corrections on the left-hand pages before sending a manuscript to be typed.
Professor Ortega called Mr. Fuentes “an unleashed cultural force” who avoided some of the trappings of literary celebrity. Indeed, in a retrospective book that he wrote about Mr. Fuentes’s life when the writer turned 80 in 2008, Mr. Ortega wrote, “Fuentes detests the literary life, its obligations and commitments.”
“He hasn’t created his own group, and he belongs neither to parties nor ideologies,” Mr. Ortega added. “He isn’t controlled by either the power of the state nor the power of the market.”
Mr. Fuentes’s independent thought and reputation for supporting leftist causes led to his being denied visas to enter the United States in the early 1960s. When he was refused permission to come to New York in 1963 for a presentation of an English translation of one of his books, he reacted angrily, saying, “The real bombs are my books, not me.”
Congress intervened in 1967, and the restrictions against him were lifted. In subsequent years he traveled to the United States frequently, spending time teaching at several Ivy League universities.
Mr. Fuentes is survived by his wife, Silvia Lemus, and a daughter, Cecilia, by a previous marriage to the actress Rita Macedo, who died in 1973. Two children from his marriage to Ms. Lemus, Carlos and Natasha, died before him.
For much of his career Mr. Fuentes competed for recognition and influence in Mexico and abroad with another titan of Mexican letters, the poet Octavio Paz. Mr. Paz won the Nobel Prize in Literature in 1990, but Mr. Fuentes, a perennial on the short list for the honor, never did.
The two became friends in 1950, when Mr. Paz published his landmark work on Mexican identity, “The Labyrinth of Solitude.” They grew closer as they worked together on several literary projects, but by the mid-1980s their political opinions had started to differ. Mr. Fuentes supported the Sandinistas, the leftist rebel group in Nicaragua, but Mr. Paz, who had more conservative views, condemned them. Then, in 1988, the literary magazine Vuelta, which Mr. Paz directed, published an article that was fiercely critical of Mr. Fuentes, accusing him of lacking true Mexican identity. That set off a bitter and often public feud that lasted until Mr. Paz died in 1998. Neither man apologized, diminishing the reputations of both.
Still, in his later years, Mr. Fuentes became an elder statesman of international letters, living in both London and Mexico City, spending part of the year at American universities and lecturing widely. On his 80th birthday, hundreds of admirers gathered at the Metropolitan Museum of Art in New York to celebrate his life and work. He was introduced by Ruben Beltran, the consul general of Mexico in New York at the time.
“To speak about Carlos Fuentes is to engage inexorably in Mexican history and culture,” Mr. Beltran said. “We cannot fathom a debate on Mexican literary and humanistic traditions in which his name and work are absent.”