As is tradition, the singer lined up with the rest of the acts to be greeted by the royals, following the annual Christmas show.
As Prince Charles and Camilla introduced themselves to Gaga, the Duchess then revealed a surprising thing they have in common.
”My grandchildren call me Gaga,” she told the ‘Perfect Illusion’ singer (according to ITV News).
Gaga was a surprise performer at the Royal Variety, which this year was hosted by David Walliams.
She sang a rendition of her latest single ‘A Million Reasons’, which she also showcased on ‘The X Factor’ last weekend.
There was comedy from Joe Lycett, Alan Davies and Rob Beckett, while The Beatles Cirque Du Soleil’s LOVE show flew in from Las Vegas for a special performance.
There were also showcases from the cast of musicals ‘Dreamgirls’, ‘An American In Paris’ and ‘The Girls’, both of which open in the West End in 2017.
Her did a very special card trick where Prince Charles joined him on stage, earning him a standing ovation.
Former ‘BGT’ winners Diversity also returned, seven years after their Royal Variety debut.
The Royal Variety Performance airs on Tuesday 13 December at 7.30pm on ITV.