HBO has ordered a fifth and sixth season of “Game of Thrones,”  HBO Programming president Michael Lombardo announced today.

The immensely popular medieval-style fantasy drama based on George R.R. Martin’s books returned Sunday with a ratings bonanza that drew HBO’s largest audience numbers since the finale of “The Sopranos” in 2007, (and incidentally, record levels of online piracy). It’s also been a marketing blitz for the premium cable channel, which has more than 60 licensing partners selling “Game of Thrones”-themed merchandise.

“’Game of Thrones’ is a phenomenon like no other,” noted Lombardo. “[Series creators] David Benioff and D.B. Weiss, along with their talented collaborators, continue to surpass themselves, and we look forward to more of their dazzling storytelling.”

The show’s increase in popularity has not weakened its roots in the fantasy genre, argued Variety TV critic Brian Lowry in his review of the season four premiere.

“Success hasn’t spoiled the HBO series, but rather enriched it — rendering the sets and visual effects seemingly more sumptuous, and the array of gaudy British talent within the sprawling cast even deeper,” Lowry wrote.

“Game of Thrones” is executive produced by Benioff, Weiss, Carolyn Strauss, Frank Doelger and Bernadette Caulfield. Co-executive producers are Guymon Casady, Vince Gerardis and George R.R. Martin. Producers, Chris Newman and Greg Spence.

The show airs at 9 p.m. Sundays on HBO.