This year's biggest star was sitting on stage when she was surprised by host Matt Lauer with the news that Aretha and pop star Ariana Grande were going to sing for her.
Microphones were handed to both, but once Aretha started singing, Ariana wisely let her have the floor, and it was magnificent.
The birthday girl admitted afterwards she had been overwhelmed by this gesture, tweeting:
"Aretha Franklin just sang 'Happy Birthday' to me and it will take me decades to recover. #goals"
Taylor Swift was visibly moved by Aretha's surprise performance for her
The surprise happened at the Billboard Women in Music luncheon on Friday, one day before Taylor's landmark birthday, where she also scooped the award for Billboard Woman of the Year.
Aretha's voice was in fine form
She told the crowd, "Being named Billboard Woman of the Year for a second time is this amazing early birthday present.
"I turn 25 at midnight tonight, and I fully intend to celebrate like it's 1989 [the title of her latest album]. I knew it was a bad joke when I wrote it, and I just did it anyway!"