A NYC private equity manager is demanding in a new lawsuit his hedge funder ex-fiancee return the $150,000, 6.3-carat oval diamond ring he gave her in happier times — or hand over the dough he paid for it.

Luis Trevino, 38, a senior managing director at Manhattan-based Beamonte Investments, wants a judge to declare the ring he gave Laura Costanzo his property, he said in a lawsuit filed Aug. 21 in Manhattan Supreme Court.

The pair met on Valentine’s Day in 2024, and by November, Trevino was already shopping for a ring, according to court papers.

Trevino proposed to Costanzo, 37, the treasury manager at hedge fund Moore Capital Management, in front of a “Marry Me” sign while the couple was vacationing in Jackson Hole, WY on Jan. 11, the court docs say.

And he even hired a professional photographer to capture the joyous moment, according to the lawsuit.

Soon after, the couple started planning for their big day, and agreed early on about the need for a prenuptial agreement, Trevino alleged in the lawsuit.

But the relationship nosedived “after months of constant criticism and emotional distance,” Trevino told The Post through his publicist, Angélica Cabrera. “At one point, my former fiancée disappeared for an entire weekend without explanation, which made me realize that, for my own mental well-being, I needed to move on.”

His publicist told The Post Trevino does not believe Costanzo strayed.

He ended their engagement April 28.

Engagement rings are considered “conditional gifts” in New York — contingent upon the ‘I do’s’ being exchanged.

Trevino claims in court docs he is still providing for his ex, paying the rent for the three-bedroom apartment they once shared in Tribeca.

“Instead of resolving the matter amicably, I have been questioned regarding my original intentions to marry, which were rooted in the goal of starting a family,” Trevino told The Post . “My patience and generosity have been met with further demands and hostility, turning this complex and heartbreaking situation into an even more difficult ordeal. I had hoped for a private resolution. However, I now need to stand firm and advocate for myself.

“My priority now is to focus on my businesses,” including several restaurants, “and to build the future I deserve, with integrity,” it continued. “Ultimately, I am committed to moving forward with dignity while wishing her all the best.”

“Instead of resolving the matter amicably, I have been questioned regarding my original intentions to marry, which were rooted in the goal of starting a family,” Trevino told The Post . “My patience and generosity have been met with further demands and hostility, turning this complex and heartbreaking situation into an even more difficult ordeal. I had hoped for a private resolution. However, I now need to stand firm and advocate for myself.

Costanzo’s attorney, Harriet Newman Cohen, said Trevino’s version of “this story is both inaccurate and not newsworthy. As it concerns a private matter, we will not be providing further comment or coverage. We can confirm that numerous settlement proposals have already been extended.”