Britain's Prince William and his children, Prince George and Princess Charlotte, celebrated his 42nd birthday at Taylor Swift's Wembley Stadium concert on Friday.
CNN reported that Swift and her boyfriend, NFL star Travis Kelce, 34, also greeted the royals backstage.
Swift, 34, shared a photo of her Kelce and the family on her social media accounts.
"Happy Bday M8! London shows are off to a splendid start," she wrote.
The post has already gotten nearly 7 million "likes" on her account.
The official Prince and Prince of Wales Instagram account shared a similar photo.
"Thank you @taylorswift for a great evening! #LondonTSTheErastour," the portrait was captioned.
It has gotten more than 2 million "likes."
Also among the celebrities at the 88,000-person crowd at the stadium were Nicola Coughlan, Cara Delevingne, Salma Hayek, Leslie Mann and Jonathan Van Ness.
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Noticeably missing from the big night out was William's 42-year-old wife, Kate Middleton, who has been making few public appearances as she battles cancer.
She was most recently seen briefly at last week's Trooping the Color event celebrating her father-in-law, King Charles' 75th birthday.