The epic tale of treachery among a series of families vying for power in a medieval-style world is currently on its fourth series - shown on Sky Atlantic in the UK.
Michael Lombardo, president of US broadcaster HBO Programming, who make the show, said it was "a phenomenon like no other" and said the cast and crew "continue to surpass themselves".
He said: "We look forward to more of their dazzling storytelling."
The series, filmed on location around the world including Scotland and Northern Ireland, is based on the best-selling books by George RR Martin.
Familiar faces in the current cast include Lena Headey, Charles Dance, Aidan Gillen and Diana Rigg.
The premiere of the new series was watched by an average of 6.6 million people in the US with 1 million tuning in in the UK.