The England international had been frustrated by his former club for much of the showpiece occasion in his homeland, but Madrid once more found a way to win in the Champions League.
Dani Carvajal headed in from a corner before Bellingham teed up Vinicius Junior to fire into the far corner to deliver Madrid's 15th European Cup.
"I have always dreamed of playing in these games," an emotional Bellingham told TNT Sports. "You go through life and there are so many people who say you cannot do things. I was alright until I saw my mum and dad's face.
"My little brother is there and I'm trying to be a role model for him. I cannot put it into words. The best night of my life."
The England international and his team-mates struggled to create anything against a dominant Dortmund for much of the game.
"I have to be honest, they were the better team in the first half," Bellingham told DAZN.
"They could have been two or three up, but it's just that character... (Madrid can) come back to haunt you."
The midfielder paid credit to his former side Dortmund for playing their part in his journey to the game's summit.
"Huge respect for both clubs - the club I'm at now is so special to me and so is my old club," continued the 20-year-old.
"It wouldn’t be possible without them. I'll always be grateful and always have respect for what that club did for me."
Carvajal was an unlikely hero as the right-back along with Nacho Fernandez, Luka Modric and Toni Kroos, in the final game of his club career, joined Madrid legend Paco Gento as the only players to win the competition six times.
The Spanish international admitted his side had ridden their luck during a dominant first 45 minutes from Dortmund, who struck the post through Niclas Fullkrug.
"We knew it would be a tough game, and the first half they were very superior but we got out alive," said Carvajal.
"We knew our moment would come, and it did, and we have the 15th."
Midfielder Kroos set up Carvajal's opener and impressed on his final appearance for the club ahead of retirement this summer.
"Kroos has finished his career in the best way, everybody wanted him to retire like this," Ancelotti told TVE.
"It's a fantastic career - we're very sad but we have to respect it."
The Italian coach pledged there would be big celebrations on Sunday back in the Spanish capital.
"Tomorrow (I'll have a) cigar, sunglasses, we sing, we dance, we'll do it all," said the jubilant coach.
