Who is Katherine Zhu, PGA champ Collin Morikawa’s girlfriend?

Katherine Zhu has always been “proud” of boyfriend Collin Morikawa, long before the 23-year-old won the PGA Championship on Sunday.

Last month, fellow golfer Zhu praised Morikawa on social media after he captured the Workday Charity Open and Barracuda Championship titles.

“From playing US Amateur in college to winning two PGA Tour events. So freaking proud of you! I love you @collin_morikawa,” Zhu posted to Instagram.

On Sunday, Zhu — who also caddies for Morikawa — celebrated the golfer’s PGA Championship at TPC Harding Park in San Francisco as they posed alongside the Wanamaker Trophy. Morikawa finished with a 13-under par following an epic drive on the 16th hole.

“It’s been a life goal since I was a kid,” Morikawa said after the tournament. “This is what I always wanted to do. I feel very comfortable in this spot. When I woke up today, I was like, ‘This is meant to be. This is where I feel very comfortable. This is where I want to be, and I’m not scared from it.’”

What is also “meant to be” is Morikawa’s romance with Zhu.

A Pepperdine University athlete, 24-year-old Zhu is said to have met Morikawa, a UC Berkley alum, through college golf. In March, the couple celebrated their three-year anniversary.

Earlier this year, Morikawa quipped that Zhu “beats [him] probably on 70 percent of our chipping competitions.”

“I think that’s what’s great about her is that we’re always competing. I think the PGA Tour is awesome like that. To have her around when we’re in the off weeks, and no one is around. She can always bring a wedge to the course, and we can always do something fun,” he said.

In addition to getting playful on the course, Zhu — a self-proclaimed “dog lover” — also shares scenic selfies regularly on Instagram, as well as posting her own golfing photos and videos. In January, Zhu also posted a shot of her encounter with Tiger Woods.

“All I said last week was ‘I can’t see’ but it’s okay cause this happened…,” Zhu captioned the photo.

As for Morikawa, who netted nearly $2 million from Sunday’s win, he continues to be Zhu’s No.1 fan.

“First like ❤️,” he responded to her bikini post in July.