Publisher Penguin Group (USA) announced Wednesday that Clancy died Tuesday in Baltimore. There was no immediate word on a cause of death.
Clancy wrote dozens of books, including "The Hunt for Red October," "Clear and Present Danger" and "The Sum of All Fears."
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. Several of his books were later made into movies.
The Baltimore native worked at an insurance agency before he turned writing into a full-time job.
Clancy is survived by four children from his first marriage and a wife, Alexandra Marie Llewellyn, whom he married in 1999.
Penguin Group (USA)'s executive David Shanks, who was personally involved in the publication of every one of Clancy's books, said, "I'm deeply saddened by Tom's passing. He was a consummate author, creating the modern-day thriller, and was one of the most visionary storytellers of our time. I will miss him dearly and he will be missed by tens of millions of readers worldwide."
The Associated Press and ABC News contributed to this report.