"Game of Thrones" has an average audience of 18.4 million, outranking "The Sopranos." Helen Sloan / HBO With two episodes remaining in the fourth season of Game of Thrones, the show has now become the most popular series in HBO's history.

Episodes of the show, which debut Sunday nights (9:00-10:00 p.m. ET/PT), have an average gross audience of 18.4 million viewers, surpassing the previous record set by the 2002 season of The Sopranos, which had an average gross audience of 18.2 million viewers per episode. Season 3 of Game of Thrones had an average gross audience of 14.4 million viewers per episode.

The next episode of Game of Thrones debuts Sunday, June 8, followed by the season finale Sunday, June 15.

Based on the bestselling fantasy book series by George R.R. Martin, Game of Thrones is an epic story of treachery and nobility set on the continent of Westeros, where summers and winters can last years, and only the lust for power is eternal. The Emmy- and Golden Globe-winning series was recently renewed for a fifth and sixth season.

Season 4 credits: The executive producers of Game of Thrones are David Benioff, D.B. Weiss, Carolyn Strauss, Frank Doelger and Bernadette Caulfield; co-executive producers, Guymon Casady, Vince Gerardis and George R.R. Martin; producers, Chris Newman and Greg Spence.