Game of Thrones is coming to the stage, with a theatre adaptation likely to be a major attraction in the West End and on Broadway.
The show will open in 2023 and depict a pivotal gathering more than a decade before the events in George RR Martin's novels and the hit TV series.
Some of the best-known characters from the epic story will be involved.
The show will be brought to life by the British pair of playwright Duncan MacMillan and director Dominic Cooke.
"The production will boast a story centred around love, vengeance, madness and the dangers of dealing in prophecy, in the process revealing secrets and lies that have only been hinted at until now," a statement said.
The stage show, set during a grand jousting tournament that helped set in motion the subsequent events, "ought to be spectacular", Martin said.
"The seeds of war are often planted in times of peace," he said.
"Few in Westeros knew the carnage to come when highborn and smallfolk alike gathered at Harrenhal to watch the finest knights of the realm compete in a great tourney, during the Year of the False Spring.
"It is a tourney oft referred during HBO's Game of Thrones and in my novels, A Song of Ice and Fire.
"And now at last, we can tell the whole story... on the stage."
Characters who were present and went on to be major figures in the books and TV show include Robert Baratheon and Jaime Lannister.
The author said starting work with MacMillan and Cooke before the pandemic had been "a treat - and I am eager for our collaboration to resume".
"Our dream is to bring Westeros to Broadway, to the West End, to Australia... and eventually, to a stage near you," he added.
MacMillan, whose plays include Lungs; People, Places and Things, and 1984, said: "I have such admiration for George's world and his characters.
"His generosity and trust during this process has been incredible.
"Working on this play during lockdown has felt like a real privilege.
"I can't wait until we can be back in a theatre to experience this together."
Cooke was artistic director of London's Royal Court Theatre from 2007-13 and directed The Hollow Crown: The Wars of the Roses, a TV adaptation of a series of Shakespeare's plays.
"One of George's inspirations for the original books was Shakespeare's history plays, so the material lends itself naturally to the theatre," the director said.
"Duncan MacMillan and I are having a great time digging into the dynastic power struggles at the heart of George's extraordinary imaginative world - and he has been hugely generous and supportive towards both of us."
The announcement came after the news Martin has signed a five-year deal to develop more TV shows for HBO.
A prequel series, House of the Dragon, set 300 years before the events of Game of Thrones, is expected to air next year, while several other TV spin-offs are also already in the works.