New York Yankees ace Nestor Cortes had a hell of an experience on the mound at his first All-Star Game -- and then he got engaged to his girlfriend!!

The left-handed pitcher just shared the news on his social media page ... saying following his dominant outing in Tuesday night's midsummer classic, he proposed to his GF -- and she said yes.

"All Star week made 2 of my dreams come true," the 27-year-old said. "Pitch in a all star game. And propose to my bestfriend. With my parents along my side. I had to make us official."

Alondra G. Esteras Russy confirmed on her own social media that she didn't turn the Yanks star down ... writing on pics of her new ring, "Of course i said YES !"

Cortes appeared to pop the question at the Los Angeles County Museum of Art -- a fitting place, considering the paint he had thrown at the All-Star Game just hours earlier.

In his one inning of work, he struck out two, allowed no hits and gave up no runs -- as he helped propel the American League to a 3-2 win over the National League.

Only thing that could make this year better would be a World Series ring -- and, given the way the Yankees look, that might just happen.