Welcome to Ralph’s Club, only open for one night. And what a dazzling establishment it is.

America’s ultimate aspirational lifestyle designer, Ralph Lauren, didn’t just rent a room for his show – he built an entire black-and-white Art Deco-inspired nightclub in a former bank on Wall Street and asked his 230 guests to keep costuming to the same colors. From the ornate, three-tiered chandeliers to the sunrise mirrors, silvered columns and skyscraper-lit lights, his team created a Gatsby-esque after-hours hotspot. Only the original double-curved staircase remained un-Ralphed.

Several hundred guests, including Cate Blanchett, Mandy Moore and Henry Golding, sat at tables imbibing and eating with ease while models such as Gigi Hadid and Bella Hadid sauntered through the space in variations on the traditional tuxedo and gown. Following the runway portion of the evening’s events, Lauren earned a standing ovation when he ascended into the space.

Janelle Monáe, who famously dresses almost exclusively in the same standard palette and wore a tuxedo in the music video for her 2010 hit, “Tightrope,” served up the evening’s entertainment while keeping with the black-tie theme.

“I think you really, truly are the most amazing American designer we have,” she told the designer during her performance. She then electrified the crowd, standing on a chair, flinging potato chips and wine in the air, crawling along the floor, and tossing up a shoe – all while belting out a song.

“This one right here is the best club I’ve ever been to,” model, actress and University of Southern California communications student Sistine Stallone told The Post. The middle daughter of Sylvester Stallone and Jennifer Flavin lamented the fact that she never mastered ballroom dancing, despite her mother’s best efforts. “I did cotillion for six years,” she said. “I don’t know how I didn’t learn anything!”

Rapper and singer Jidenna, who was resplendent in an embellished black Ralph Lauren tux, is a big fan of clubs. “There was a specific club, where you go and you get everything for cheap when I was a kid – and that’s Sam’s Club. But Ralph’s Club is nice. It’s swanky!”