Saul “Canelo” Alvarez has a new belt in his collection…

The 21-year-old Mexican boxer won the WBA championship belt by unanimously outpointing Austin Trout on Saturday night at San Antonio’s Alamodome.

Alvarez (42-0-1) unified the 154-pound titles with a dominant victory, retaining his WBC super welterweight championship along with the vacant Ring Magazine belt. But it was the WBA belt that was the ultimate prize.

Alvarez received winning scores of 115-112, 116-111 and 118-109 to beat Trout.

Some observers speculated Alvarez wasn’t ready for a veteran opponent like Trout (26-1), but they didn’t realize how personal the bout was to him.

“My brother was a big motivation for this,” Alvarez said. “I did this for him. He beat my brother, and that’s my blood.”

Alvarez fought like a man out for revenge, knocking down Trout for the first time in his career and staggering him several times to the delight of the crowd that continually chanted “Mexico! Mexico!”

“I’ll take the loss like a man,” Trout said. “The better man won tonight. He was better than me. I have no excuses.”

Trout was the more active fighter, connecting on 154 of 769 punches compared to 124 of 431, but Alvarez landed 43 percent of his power punches compared to 27 percent for Trout.

“He shocked us, I was prepared for a different fighter,” Trout said. “I tried to pressure the action and change things up, but he kept changing.”

Alvarez dropped Trout early in the seventh round, catching the southpaw flush to the chin with a powerful straight punch. Trout staggered a few steps backward before falling front first to the canvas.

“He caught me with a good shot,” Trout said. “There is nothing else I can say.”