These new films are not to be tied to the ongoing 'Skywalker' saga of the "Episodes" movies or be connected to the trilogy being developed by filmmaker Rian Johnson, reported Entertainment Weekly.
"David and Dan are some of the best storytellers working today," said Kathleen Kennedy, president of Lucasfilm.
"Their command of complex characters, depth of story and richness of mythology will break new ground and boldly push Star Wars in ways I find incredibly exciting."
It is a major project for both Benioff and Weiss, who have become stars in their own right after the massive success of the fantasy TV series.
"In the summer of 1977 we traveled to a galaxy far, far away, and we've been dreaming of it ever since," Benioff and Weiss said in a joint statement.
"We are honored by the opportunity, a little terrified by the responsibility, and so excited to get started as soon as the final season of Game of Thrones is complete."
The duo are also working on "Confederate" for HBO. The show is an alternate history series about an America in which the South won the Civil War but the show has faced a lot of criticism.
The final season of "Game of Thrones" is set to air in 2019.