The two singers have been at odds ever since critics suggested GaGa's hit "Born This Way" was heavily inspired by Madonna's "Express Yourself" - and the "Material Girl" agreed.
The "Poker Face" singer made matters worse in 2016 by insisting the comparisons were "ridiculous" and then pointing out that she played her own instruments, while Madonna didn't.
"Madonna and I are very different," she said. "I wouldn't make that comparison at all. I don't mean to disrespect Madonna... She's the biggest pop star of all time... But I play a lot of instruments. I write all my own music. I spend hours and hours a day in the studio. I'm a producer. I'm a writer. What I do is different."
Madonna responded by sharing a meme of former U.S. presidential candidate Hillary Clinton looking at her phone with the text reading, "Can't hear you. Too busy being awesome."
The singer added the caption, "Like a boss! LOL."
But the two stars looked like old friends as GaGa turned up to Madonna and Guy Oseary's Oscars after-party in Los Angeles.
Despite a firm ban on social media posts, one shot of the two stars leaked, and it was clear that all was forgiven.
terrifying pic.twitter.com/hBz0IlK3fh— Rose Dommu (@rosedommu) 25 February 2019
Madonna, wearing a diamond veil and a beige silk Indian dress and sporting braided blonde hair, hugged GaGa, who was still wearing her black Oscars dress, as she clutched her first Academy Award for Best Song.