Thomas Leo Clancy Junior was born to Thomas and Catherine in Baltimore, Maryland. He grew up in Maryland attending school at Catherine Loyola Blakefield in Towson, Maryland alongside two siblings. After completion of High School, Clancy applied to and attended Loyola University in Chicago. He studied English Literature. Clancy's first run in with the military happened while studying at Loyola. He applied for the Army Reserve Officers Training Corps, but he got rejected due to his poor eyesight.  Though Clancy got rejected, he never lost his dream to serve in the military.  This is the inspiration for the countless novels that he has written over his years. After graduating, Clancy was recruited to work at O. F. Bowen Agency. During his time at the agency, Clancy would find his love for writing. This led him to write his first and one of his best novels, The Hunt for Red October. After seven years at the agency, Clancy bought the company, all while living his double life as an author. 

Clancy began writing The Hunt for Red October in 1982, and he finished the book in 1984. He then got the book published by the Naval Institute Press. All the while, Clancy never had a literary Agent, and he was able to publish a book that had four press runs and hit best-seller lists in Washington, San Francisco, and New York City all within a year of publishing the book. In this book, Clancy was able to establish one of his best-known characters, Jack Ryan. The Hunt for Red October managed to get presidential acclaim by Ronald Reagan. This slingshot the book into the limelight of the nation, easily making it a national bestseller.  After the success of the book, Clancy became a common household name. He was praised highly by critics who noted his technical know-how and extreme accuracy and realism that he brought to the page. His success made his insurance job take a backseat which allowed him to focus heavily on his writing. This would lead to his next best seller Red Storm Rising.

After the success of The Hunt for Red October, Clancy began writing and publishing a book every one to two years. All of his books stayed in the realm of fiction until his release of Submarine: A Guided Tour Inside a Nuclear Warship.  This began Clancy's fascination with nonfiction books. He enjoyed writing nonfiction books that delved deeply into the various branches of the military because of his lifelong fascination with joining the military. Clancy enjoyed writing these books about as much as his own nonfiction books because he had a deep appreciation of the military. Many of Clancy's books will even stand the test of time through an ever-expanding television presence as well as many video game adaptations. Several of Clancy's books managed to become highly grossing films, namely The Hunt for Red October and Clear and Present Danger. All of this acclaim grossed Clancy a substantial amount of money. At the time of his death Clancy was worth nearly $190 million dollars. The majority of that money came from his many novels. 

Clancy's hyper realistic novels had a lot of acclaim, but how did Clancy manage to find out all of his information without ever holding a military position? Well, he just managed to make many friends in very high places. Clancy would often dine with presidents, meet with Admirals and Generals that could show him around ships and bases, and he even got invited a multitude of times to the Pentagon by top officials. All of these people were able to give Clancy insight into the many aspects of being in the United States Armed Services. Many Pentagon officials would even fill him in regularly with new breaking news so he could constantly be thinking of and creating new ideas with the most current information available. Many of Clancy's novels were received highly enough that they were even mandatory reads for cadets at various military academies. 

Throughout Clancy's life, he managed his time between writing his own novels, writing novels with other authors, and work and oversee his insurance agency for many years. Even through his busy schedule, Clancy always made room for his love life and children. Clancy's first wife was Wanda Thomas King. They got married in 1969, and they had four wonderful children together. Unfortunately, Clancy and King would separate in 1996, but they would not get divorced, legally, until 1999. In this time period Clancy met a women named Alexandra Marie Llewellyn. They met in 1997 and six months after his divorce from King, he married her. He would go on to have one kid with Llewellyn to total his kids out at five. These two remained together until his death from an unknown illness on October 1st, 2013. It involved a failing heart, but the illness was never explicitly stated.