The joint-leads of A Star Is Born took to the stage to perform an incredibly intimate and shockingly sensual rendition of Shallow, leaving audience and viewers squirming in their seats as speculation grows about their intense chemistry - despite Cooper being in a longterm relationship with the mother of his child, Russian supermodel Irina Shayk.
Taking to Instagram, Gaga - born Stefani Joanna Angelina Germanotta - shared a photo of the duo on stage at the Academy Awards and gave a glowing mention to her director and co-star.
WATCH: Lady Gaga and Bradley Cooper perform Shallow at the Oscars here!
"Nothing could be more special than sharing this moment at the Oscars with a true friend and artistic genius," she captioned the shot, which shows the pair sitting side by side a the piano with Cooper's arm wrapped tightly round her waist.
The post quickly racked up more than 2.5 million likes and thousands of comments, with one user tellingly remarking: "Yes okay, he's 'only a friend', but your eyes are falling in love."
"Whether romantic or platonic, this is what soulmates looks like," a woman said.
"You guys have a beautiful connection - the two of you belong together as more than friends," another wrote.
However a number of comments claimed the display was "distasteful and disrespectful" to Irina, with one person asking: "So it's alright and celebrated these days to fall in love with a taken man?"
Gaga's post comes hours after exclusive photos obtained by Daily Mail showed the co-stars looking tactile as they chatted and embraced one another at the Warner Bros Post-Oscars party while Irina sat alone just inches away.
According to a Daily Mail source who attended the elite gathering, after scooping the Oscar for Best Song Lady Gaga arrived at the bash and "made a beeline for Bradley" who was already there with Russian catwalk queen Irina and his mother Gloria.
The insider revealed the co-stars hugged repeatedly and spoke into each other's ear, adding "they were all over each other - they couldn't get enough of each other".
Gaga reportedly chatted with Cooper for almost two hours while Irina watched from the sidelines, looking unimpressed as she snacked on appetisers.
For the exclusive pictures, click here.
Bradley and Irina have been together since 2015 and share almost two-year-old daughter Lea De Seine Shayk Cooper.