Hamptons homeowners hoping to cash in on deep-pocketed golf fans during next month’s US Open are discovering that $100,000-a-week rental dreams may have overshot.

Rental prices across the ritzy beach enclave are slipping ahead of the June 18-21 tournament at Shinnecock Hills Golf Club as inventory piles up and demand falls short of expectations, as Bloomberg News first reported.

Average nightly rates during the championship rounds are down 2.5% from the same period last year to $1,106, according to data from vacation rental analytics firm AirDNA cited by Bloomberg. Available listings are up 17.5% year over year.

“The problem is very simple. Too many owners thought that the US Open would automatically mean a six-figure payday, and so the market got flooded with inventory,” luxury real estate broker and “Million Dollar Listing Los Angeles” star Josh Flagg told The Post.

“Luxury renters are still spending, but they’ve become much more value conscious,” he added. “They won’t overpay just because there’s a sporting event in town.”

Flagg, who splits his time between Los Angeles and New York and recently bought a home in East Hampton, said the sudden flood of listings undermined the exclusivity that normally drives Hamptons pricing.

“The Hamptons rental market runs on scarcity,” he explained. “Once everyone lists at once, pricing power disappears.”

In Hampton Bays, which has seen the steepest drop in demand, travelers can still snag a studio apartment for as little as $154 a night, while larger six-bedroom villas top out around $5,325.

In nearby Southampton, the tournament’s host town, rentals range from $233 per night to as much as $7,376 for sprawling luxury homes, according to AirDNA.

One seven-bedroom Southampton estate on nearly two acres hit the market seeking a jaw-dropping $200,000 for a short-term US Open stay.

Some landlords farther east in Sag Harbor have been asking $100,000 or more for a single tournament week — rates typically reserved for the entire month of July.

But many of those sky-high listings remain unrented.

“We are finding that there isn’t as much demand as you would expect,” Judi Desiderio, managing partner at William Raveis Real Estate in the Hamptons, told Bloomberg News.

“So last-minute bookers can get house rentals at a relative bargain.”

The softening market marks a rare crack in one of the country’s most notoriously expensive summer rental destinations, long favored by Wall Street moguls and celebs willing to shell out eye-watering sums for beachfront escapes.

“For as many homes that are rented, there are just as many homes that go unrented,” real estate agent Robert Banker of Hedgerow Exclusive told Bloomberg.

“There’s 150 rentals for $100,000 in Sag Harbor. There’s a delusion that you’re sitting on a lottery ticket and it’s just not coming.”

The mismatch between expectations and reality comes as broader economic uncertainty and geopolitical turmoil have cooled enthusiasm around some of the world’s biggest sporting events, Bloomberg noted.

The FIFA World Cup, which kicks off this summer across North America, has seen weaker-than-expected demand for hotels and short-term rentals in host cities.

Even so, the Hamptons remain staggeringly expensive by almost any measure.

Average nightly summer rates for July and August still range from $903 in Hampton Bays to $1,730 in Southampton, according to AirDNA.

Booking revenue for the full Memorial Day-to-Labor Day stretch is projected to climb nearly 11% from last year to roughly $121 million.

AirDNA economist Bram Gallagher said Hampton Bays has emerged as the hottest booking market for the tournament week largely because it offers relatively cheaper options than Southampton and neighboring villages.

Homeowners are also trying to capitalize on a recent rule change tied to the US Open that reduced the minimum rental stay from two weeks to just three days — giving renters more flexibility but increasing pressure on landlords to fill vacant nights.