Big changes are underway at Lucasfilm ... because studio president Kathleen Kennedy is stepping down after nearly 14 years ... and George Lucas protege, Dave Filoni, is stepping up as the creative leader.

Lucasfilm and Walt Disney Studios announced the leadership changes Thursday ... revealing Lynwen Brennan as the new co-president.

Filoni -- who worked with George on "Star Wars: The Clone Wars" and helped Jon Favreau launch "The Mandalorian" -- will serve as President and Chief Content Officer.

Kathleen's exit isn't a huge shock ... it had long been expected in Hollywood.

Lucasfilm says Filoni's "close collaboration" with George "will carry Lucasfilm into its next chapter of storytelling, with a strong foundation of creative vision and operational leadership guiding the studio forward."

Kathleen will return to being a movie producer full-time, Lucasfilm says, including the upcoming movies "The Mandalorian and Grogu" and "Star Wars: Starfighter."

She joined Lucasfilm in 2012 as co-chair alongside George ... and a few months later, she was promoted to president after Disney shelled out $4 BILLION for Lucasfilm.