The annual honour is presented to a "critically acclaimed author whose work embodies PEN America's mission to oppose repression in any form and to champion the best of humanity."
Past winners include J K Rowling, Salman Rushdie, and Margaret Atwood.
"No stranger to the dark side, Stephen King has inspired us to stand up to sinister forces through his rich prose, his generous philanthropy, and his outspoken defense of free expression. Stephen has fearlessly used his bully pulpit as one of our country's best-loved writers to speak out about the mounting threats to free expression and democracy that are endemic to our times.
King will be honoured on May 22 at the 2018 PEN America Literary Gala, the same day his latest novel, "The Outsiders", will release.