Penguin Group (USA) said Wednesday that Clancy died Tuesday in Baltimore. The publisher did not disclose a cause of death.
Clancy arrived on best-seller lists in 1984 with "The Hunt for Red October." He sold the manuscript to the first publisher he tried, the Naval Institute Press, which had never bought original fiction.
A string of other best-sellers soon followed, including "Red Storm Rising," ''Patriot Games," ''The Cardinal of the Kremlin," ''Clear and Present Danger," ''The Sum of All Fears," and "Without Remorse."
Clancy had said his dream had been simply to publish a book, hopefully a good one, so that he would be in the Library of Congress catalog. Several of his books were later made into movies, with the latest, based on desk-jockey CIA hero "Jack Ryan," set for release later this year.
His 17th novel, "Command Authority," is due out that same month from G.P. Putnam's Sons.
Born in Baltimore on April 12, 1947 to a mailman and his wife, Clancy entered Loyola College as a physics major, but switched to English as a sophomore, saying later that he wasn't smart enough for the rigors of science.
Ironically, his novels carried stiff doses of scientific data and military detail.
After graduation in 1969, he married his wife Wanda and joined her family's insurance business, all the while scribbling down ideas for a novel.
In 1979, Clancy began "Patriot Games," in which he invented his hero, CIA agent Jack Ryan. In 1982, he put it aside and started "The Hunt For Red October," basing it on a real incident in November 1979, in which a Soviet missile frigate called the Storozhevoy attempted to defect.
In real life, the ship didn't make it, but in Clancy's book, the defection is a success.
By a stroke of luck, President Reagan got "Red October" as a Christmas gift and quipped at a dinner that he was losing sleep because he couldn't put the book down - a statement Clancy later said helped put him on the New York Times best-seller list.
It led to a string of hits, both on the page and in Hollywood blockbusters. He even ventured into video games with the best-selling "Tom Clancy's Ghost Recon: Future Soldier," ''Tom Clancy's Splinter Cell: Conviction" and "Tom Clancy's Splinter Cell: Double Agent."
"He was a consummate author, creating the modern-day thriller, and was one of the most visionary storytellers of our time," Penguin Group (USA)'s executive David Shanks said in a statement Wednesday.
Clancy continued to play off - and sometimes almost anticipate - world events, as in the pre-9/11 paranoid thriller "Debt of Honor," in which a jumbo jet destroys the U.S. Capitol during a joint meeting of Congress.
The latest Jack Ryan movie, directed by Kenneth Branagh and starring Chris Pine, is set for release in the U.S. on Christmas Day. Keira Knightly plays Jack Ryan's wife and Kevin Costner plays his mentor at the CIA.
Clancy resided in rural Calvert County, Md., and in 1993 he joined a group of investors led by Baltimore attorney Peter Angelos who bought the Baltimore Orioles from businessman Eli Jacobs.
Clancy also attempted to bring a NFL team to Baltimore in 1993, but he later dropped out of the effort.