Tom Clancy, whose complex, adrenaline-fueled military novels spawned a new genre of thrillers and made him one of the world’s best-known and best-selling authors, died on Tuesday in Baltimore. He was 66.

Mr. Clancy, who grew up in Baltimore, died at Johns Hopkins Hospital after a brief illness, his lawyer, J. W. Thompson Webb, said on Wednesday. Neither Mr. Webb nor Mr. Clancy’s longtime publisher, Ivan Held, president of G. P. Putnam’s Sons, said he knew the precise cause of death.

Mr. Clancy’s debut book, “The Hunt for Red October,” was frequently cited as one of the greatest genre novels ever written. With the book’s publication in 1984, Mr. Clancy introduced a new kind of potboiler: an espionage thriller dense with technical details about weaponry, submarines and intelligence agencies.

It found an eager readership. More than 100 million copies of his novels are in print, and a remarkable 17 have reached No. 1 on the New York Times’s best-seller list, including “Threat Vector,” released last December. Prolific until his death, Mr. Clancy had been awaiting publication of his next book, “Command Authority,” set for Dec. 3.