Act of Defiance (novel)

Act of Defiance (stylized as Tom Clancy Act of Defiance or Tom Clancy: Act of Defiance) is a techno-thriller novel, written by Brian Andrews and Jeffrey Wilson and published on May 21, 2024. It is their first book in the Jack Ryan series, which is part of the Ryanverse featuring characters created by Tom Clancy. Act of Defiance is the first of two books by Andrews and Wilson featuring Ryan to be published in the same year, the other being Defense Protocol.

In the novel, President Ryan deals with a rogue Russian nuclear submarine forty years after the events of The Hunt for Red October (1984). It debuted at number ten on the New York Times bestseller list.