We got this shot of 21 and his mom boarding the plane at a landing strip near the immigration detention center in southern Georgia where he'd been held since ICE arrested him over Super Bowl weekend.

For good reason ... the rapper had a huge grin on his face as he headed home.

21's lawyer, Alex Spiro, saw our pic and said, "That's how we take people home when they win."

We're told 21 Savage's homecoming will include a meeting with friends and family in the ATL area.

A ton of celebs voiced messages of support for the rapper while he was locked up. Kendrick Lamar, Jesse Williams, Future and Post Malone -- who sported a 21 Savage shirt at the Grammys -- were just some of the A-listers.

21's not out of the woods ... he still faces deportation. We're told his people are going to fight this tooth and nail, and it appears the big issue is whether 21 has been convicted of a felony. It's true ... 21 pled guilty to felony drug charges in 2014, but that conviction was expunged last year so there is not a felony on his record. Although ICE isn't giving us any information, it appears they still view 21 Savage as a convicted felon.

The rapper has applied for a U-Visa, having been in the U.S. more than 10 years, but the conviction seems to be the sticking point.