Heidi Klum Gifts Son Henry a Ferrari for His 21st Birthday Years After Mario Kart Bet

Heidi Klum took birthday gifts to another level ... surprising her son Henry with a Ferrari for his 21st birthday, all thanks to a wild bet he made years ago.

The supermodel captured the big reveal on video Saturday, showing Henry walking outside with his stepdad, Tom Kaulitz, before coming face-to-face with a bright red Ferrari F430 waiting for him.

Henry, stunned by the sight of the sports car, takes in his hot new ride ... while Heidi films the reaction and reminds him he's been waiting for this moment for years.

The car comes with a pretty wild backstory, too ... it was actually promised to Henry when he was a teenager. Heidi shared throwback footage explaining the deal Henry made with Tom during a game of Mario Kart.

Henry apparently won the bet 7 years ago, earning himself a promise that Tom would buy him a Ferrari when he turned 21.

The Tokio Hotel guitarist says he bought the Ferrari at an auto show last year and kept it hidden in the garage until Henry's milestone birthday.

Heidi couldn't help but marvel at the fact the promise had been made roughly 7 years earlier ... with Tom ultimately making good on his word.

Henry is one of Heidi's four children, whom she shares with ex-husband Seal. Tom married Heidi in 2019 and has become a major part of the family.