The Miami Marlins have just made a groundbreaking hire -- with the team welcoming baseball exec Kim Ng as the first female general manager in major pro sports history.

The hire makes Ng the highest-ranking woman in baseball operations among all 30 MLB teams.

51-year-old Ng started her front-office career as an intern with the Chicago White Sox in 1991 ... working her way up the ladder and becoming assistant GM to Brian Cashman with the New York Yankees in 1998.

Ng joined the Los Angeles Dodgers in 2001 ... and served as assistant GM until becoming Senior Vice President of Baseball Operations for MLB in 2011.

Ng spoke about the new gig in a statement, saying, "I entered Major League Baseball as an intern and, after decades of determination, it is the honor of my career to lead the Miami Marlins as their next general manager."

"We are building for the long-term in South Florida, developing a forward thinking, collaborative, creative baseball operation made up of incredibly talented and dedicated staff who have, over the last few years, lady great foundation for success."

She continued ... "This challenge is when I don’t take lightly. When I got into this business, it seemed unlikely a woman would lead a Major League team, but I am dogged in the pursuit of my goals."

FYI -- Ng's boss is Derek Jeter ... who, of course, was on the Yanks when she worked as assistant GM from 1998 to 2001.

Ng had interviewed to be GM for other teams like the Giants, Dodgers, Angels and more in the past ... and now she's gunning for ultimate success with her first opportunity.

"My goal is now to bring championship baseball to Miami. I am both humbled and eager to continue building the winning culture our fans expect and deserve."

Congrats!!!