Sabalenka, fresh off her first Indian Wells triumph, became the fifth woman to sweep the "Sunshine Double" of Indian Wells and Miami and the first since Iga Swiatek in 2022.
"That sounds crazy, sounds unreal," Sabalenka told Tennis Channel. "I'm just super grateful, super happy and super proud right now.
"I know Coco quite well," Sabalenka said.
"I know that she's not going to, like, give me this final easily. I knew that she's going to be fighting, she's going to be moving well, she's going to be trying to put literally every ball back on my side.
"I lost a couple of opportunities in that second set, but I was just trying to stay mentally positive going into the third set."
The Belarusian star, whose only defeat this year was her Australian Open finals loss to Elena Rybakina, handed Gauff her first career defeat in a hardcourt final.
The American had won her first nine, including a triumph over Sabalenka in the 2023 US Open championship match.
Gauff had also beaten the Belarusian for the title on the red clay of Roland Garros last year.
Sabalenka pocketed the first set with a ruthless display of power and precision.
She broke Gauff to open the match and, after Gauff saved three break points in a gritty fifth game, broke the American again in the seventh before serving it out in 37 minutes without facing a break point herself.
In a tense second set, Gauff's first break point chance - from a blistering backhand passing winner in the second game - sparked a jubilant reaction from the crowd at Hard Rock Stadium, home of the NFL's Miami Dolphins that is just about an hour away from Gauff's Delray Beach home.
But Gauff couldn't convert, slamming a forehand into the net on the next point as Sabalenka held.
It needed another gutsy hold from Gauff to keep it on serve in the fifth game.
Up 40-0, she wasted three game points with a pair of errors off the ground and a double fault then had to save a break point before taking the game on her fifth game point.
Gauff, finding more depth on her ground strokes to ramp up the pressure on Sabalenka, broke for the first time to take the second set.
But that was her last hurrah. Sabalenka broke to open the third set and broke again to seal the win when Gauff sailed a backhand long on Sabalenka's first match point.