The 'Material Girl' hitmaker showed just as much cleavage as the 'I Kissed A Girl' singer in their graffiti-inspired outfits at The Metropolitan Museum of Art's 2015 Costume Institute Benefit in New York City to celebrate the opening of the China: Through the Looking Glass exhibition.
Madonna's floor-length dress, which came with a black cape, was covered in white writing which spelt out the name of her latest album 'Rebel Heart' and was completed by a pair of black leather gloves and a gold Moschino belt which she wore across her shoulder.
The 'Roar' singer's dress was covered in more colourful graffiti style writing.
Katy also unveiled a new short, cropped hair-do on the red carpet.
When asked what the inspiration for the pixie cut was, she said: 'I asked for the Kris Jenner.'
After the event Madonna, 56, and Katy, 30, were joined by fellow pop mistress Lady GaGa.
Katy posted a selfie on Instagram of the three of them and almost broke the internet, with a caption that suggested they would be releasing a track together.
The caption read: 'dropping our single tomorrow #stolethispicfromM #MONSTERCATREBELHEARTS. (sic)'
However, it was just a joke and there is no single coming out.
Both Katy and Madonna have had feuds with the 'Born This Way' singer in the past, but the Instagram post suggested they have put their issues behind them.
Both the 'Rebel Heart' singer and 'Fireworks' hitmaker attended the exclusive event with dates. Designer Jeremy Scott joined Katy, while Madonna came with music producer Diplo.