Trank called his decision to exit the "Star Wars" universe "personal" and thanked the team of Lucasfilm and Disney for their support.
The 31-year-old "Chronicle" director further said he wanted to explore "original, creative opportunities".
"After a year of having the incredible honour of developing with the wonderful and talented people at Lucasfilm, I'm making a personal decision to move forward on a different path. I've put a tremendous amount of thought into this, and I know deep down in my heart that I want to pursue some original creative opportunities," Trank said in a statement.
Sources close to the development, however, said Trank was often indecisive and uncommunicative.
His unusual conduct during the making of Fox's upcoming "Fantastic Four" movie had apparently raised alarm among Lucasfilm executives that were entrusting him with the second Star Wars standalone film.