Stargate: Atlantis proved that Jason Momoa was one day destined for movie stardom. The Stargate franchise kicked off with the 1994 movie of the same name from director Roland Emmerich (Independence Day). It starred Kurt Russell and James Spader and followed their characters as they went through an ancient gateway to another world. The movie proved to be a hit and while there were plans for a trilogy, a sequel didn't ultimately happen.
The sprawling lore hinted at in the film suggested a much wider universe, which TV series Stargate SG-1 was only too happy to explore. Richard Dean Anderson lead the cast of this series, which picked where the movie left off while introducing new worlds and alien races. Stargate SG-1 would run for ten seasons and spawned multiple spinoffs, including Stargate: Atlantis and the short-lived Stargate Universe. While talk of rebooting the franchise pops up now and again, it's currently on hiatus.
Jason Momoa made his acting debut with Baywatch: Hawaii where he played lifeguard Jason Ioane. Once that series ended he found it hard to land other roles, but in 2005 he made his debut as Ronon Dex in Stargate: Atlantis season 2. Ronon is from the planet Sateda, which was destroyed in an attack by the Wraith. They later experimented on him, planting a tracking device in his back and turning him into a "Runner" so they can constantly hunt him for sport. This backfired badly, however, as he soon turned the tide and hunted them in return.
Following his introduction in Stargate: Atlantis season 2 episode 3, Ronon joined the team. Ronon soon became a fan favorite on the show, which is largely down to Momoa's charisma. While Ronon seemingly exists to lay the smackdown on any Wraith's he encounters, he's far from a one-dimensional action hero either. He's shown to have been deeply wounded by the loss of his homeworld and people, but throughout several seasons he comes to feel at home with his new team.
Stargate: Atlantis season 4 episode "Midway" is cited as one of his very best, with the episode essentially being a buddy comedy between him and Stargate's Teal'c (Christopher Judge, God Of War). While his performance in Games Of Thrones got him noticed, Stargate: Atlantis' Ronan Dex was an early sign Jason Momoa was destined for bigger things. It played to his action chops while also giving him interesting dramatic material to play, which is one reason his star rose dramatically when the series came to an end in 2009. Plus, he would also travel to a very different take on Atlantis in Aquaman, which cemented his stardom.