Huge stars will be on stage for the upcoming concert to help the thousands of folks who lost it all in the L.A. fires, and some of the headliners have deep L.A. roots.

Sources with direct knowledge tell TMZ, Lady Gaga, Billie Eilish and the Red Hot Chili Peppers will be among the 15 acts that have been booked so far to hit the stage 2 weeks from today.

TMZ broke the story, the benefit concert has become so big, there will be 2 venues -- the Intuit Dome and the Kia Forum, both in Inglewood.

Our sources say the initial plan was for 24 artists and bands to perform, but more than 50 have thrown their hat in the ring and that number may expand.

The concert will be streamed and organizers expect to raise millions for disaster relief.

As we reported, many of the acts will be L.A. natives, like Billie -- who was spotted Wednesday serving food to those affected by the wildfires -- and the Chili Peppers.

We're told organizers will release 15 artists shortly, so stay tuned.