HBO said Sunday?s live U.S. audience exceeded the previous series high of 16.9 million viewers.
The previous record was held by the Season 7 finale two years ago, says Reuters.
Sunday?s premiere was also the most-tweeted-about episode of the show ever.
The show had more than 5 million Tweets and 11 million mentions over the weekend.
All of the top 10 global Twitter trends late Sunday evening were about the episode.