Jason Momoa has shaved off his signature beard to promote the use of aluminium cans over plastic water bottles. Picture:Screengrab/YouTube

Jason Momoa shaved off his beard for the first time in seven years.

The 39-year-old actor said goodbye to his famous facial hair in a YouTube video posted on Wednesday, where he bid goodbye to his 'Game of Thrones' character Khal Drogo as well as his 'Aquaman' alter-ego Arthur Curry.

Speaking in the video, Jason admitted: "I think 2012 is the last time I shaved...Goodbye Drogo. Goodbye Arthur Curry."

The 'Justice League' star went on to explain that his video was not in fact about his beard but to share a message about the environment and urged his fans to "save our planet" by recycling.

He said: "Most importantly, I just want to do this to bring awareness that plastics are killing our planet.

"And if we have a solution, I don't want to bitch about it. There's only one thing that can really help our planet and save our planet as long as we recycle--and that's aluminum."

The 'Frontier' actor went on to explain that aluminum is "100% recyclable" and says he's "really kicked into gear" his own environmental mission over the past few months, including creating a line of canned water.

He continued: "About 75% of all is still in circulation today and it's 100% recyclable so you drink from the can and in about 60 days it'll be back, 100% infinitely recyclable.

"I hate going to the airport or being on the airplane and given a [plastic] water bottle when it could be an aluminum one and it could be recycled.

"About over the last two months, I've really kicked it into gear so I have a product that I'd like to take out into the world."

Jason ended his video by insisting that he's "trying his best" to "clean up" both the oceans and the land.

He said: "Aquaman is trying to do the best he can--for my kids, for your kids, for the world. Clean up the oceans, clean up the land. Love you guys."