Killer Mike and his family are breathing a collective sigh of relief … the surgery to give his son a new kidney went successfully.

Mike tells us his 21-year-old son Mikael “Pony Boy” Render came through the transplant, and “did really well.” He says Pony will be in recovery for a few hours before he’s moved back to his hospital room, but they’re already seeing some positive signs — Mike says it “looks like the kidney is already working.”

360aproko broke the story … Pony went into surgery Monday morning, after waiting 3 years for a matching organ. It’s been an ongoing health issue that Mike has been very open about.

His son’s lifesaving surgery comes on the heels of one of Mike’s most memorable days, professionally, for good and bad reasons.

As we reported, Killer Mike cleaned up at the Grammys on Sunday … winning 3 awards for Best Rap Song, Best Rap Album and Best Rap Performance — however, moments later he was in handcuffs for allegedly getting physical with a security guard at the Grammys venue, Crypto.com Arena.

Mike was booked for misdemeanor battery, and released on his own recognizance — in fact, he was still able to step out Sunday night and celebrate his Grammy wins.

All of that was firmly in his rearview, though, when the family got word Pony was cleared for surgery.

While he technically still has a criminal case on his hands, you gotta imagine he’s breathing easier now knowing his own flesh and blood came out the other side … and is doing okay.