According to fans in attendance, the 74-year-old British singer joked that "we finally found someone under 50" as he invited Rihanna to join him.
If anyone can hold their own with one of the Beatles, it’s certainly RiRi -- and did she ever! The 28-year-old singer, dressed in an over-sized striped suit, sounded incredible as she belted out the hit song.
Excited fans shared the performance on social media, including one who captioned it, in part, "legends only."
Mary McCartney, Paul's eldest daughter with the late Linda McCartney, took over her dad's Instagram for the night while also sharing snaps from the awesome set to her own account, including this close-up shot of Paul and Rihanna's duet.
The "Work" singer wasn't the only one who shared stage time with Paul. Fellow night two headliner Neil Young also joined him for a medley of "A Day in the Life," "Give Peace a Chance," and “Why Don't We Do It in the Road."
Like its counterpart, Coachella, Desert Trip took place over two weekends, and Paul took to Twitter on Sunday to thank Rihanna, Neil, and, well, everyone for the epic time he had in Southern California.
But lest you think it was just Coachella for your mom and dad, plenty of young Hollywood and A-listers were in attendance. Kate Hudson, Woody Harrelson, Emma Stone, and Mary's sister, Stella McCartney, Alessandra Ambrosio, Paris Hilton, and Busy Philipps all jammed in the desert.
This wasn't the first time Paul and Rihanna performed together live -- they also sang "FourFiveSeconds" with Kanye at the 2015 GRAMMYs -- and here's to hoping it's not the last.
Celeb fans were excited to see not just Paul and Neil but also classic rockers Bob Dylan and The Rolling Stones at the festival. Check out just how adorable Catherine Zeta-Jones and Michael Douglas were while attending weekend one with their kids: