Prince William dancing.

Just a few steps away, his 9-year-old daughter, Princess Charlotte, could be seen leaning over a railing and singing the pop track.

Prince William dancing.

Fans were thrilled to see the future king having a blast with one person commenting, “This is the best thing I’ve seen ok slay Prince William.”

Another wrote, “Prince William is the Swiftie we all needed. He is positively unhinged in the best of ways right here!”

A third, meanwhile, cheekily chimed in with a lyric from “Shake It Off,” “He’s lightening on his feet.”

William also attended the concert with his eldest son, Prince George, 10, but his youngest, Prince Louis, 6, stayed behind with his mom, Kate Middleton, who is still undergoing treatment for cancer.

The proud dad took George and Charlotte backstage to meet Swift, 34, and her boyfriend, Travis Kelce, also 34, who had flown into town to attend the Eras Tour show in the UK.

Prince William, Prince George and Princess Charlotte taking a selfie with Taylor Swift.

William, for his part, had met Swift before. In 2013, they went onstage together at the Centrepoint Gala Dinner with Jon Bon Jovi.

After her show, Swift shared a selfie via Instagram Saturday from her meeting with the prince’s kids, captioning it, “Happy Bday M8! London shows are off to a splendid start 🇬🇧🇺🇸🤝.”

The birthday wish was for William who happened to be celebrating his 42nd birthday on Friday.

Earlier in the day, Middleton, also 42, shared a playful pic of her husband having fun with their three children at the beach to commemorate his special day.

Taylor Swift and Prince William onstage with Jon Bon Jovi.

After Swift’s show, William also gave a shoutout to the “You Belong With Me” songstress, posing another photo from their meet-and-greet via Instagram Saturday.

He wrote alongside of it, “Thank you @taylorswift for a great evening! #LondonTSTheErastour.”

In the cheerful snap, Swift can be seen bending down to take a group photo with William, George and Charlotte, who all appeared to have big grins on their faces.

The “Lover” singer’s London show was not just a family affair because of the Waleses, however.

Prince William with his wife and kids at Buckingham Palace.