A rep for MGM Resorts International tells TMZ ... the singer doesn't have a $50 million gambling tab on the books with them -- even though some recently alleged the opposite. Instead, MGM came to Bruno's defense ... calling the allegation he owes a massive sum completely false.

In fact, the Las Vegas hot spot is super excited to collaborate with the Grammy winner again in the future -- not exactly the tone someone would take with a dude who's got a fat bill.

They add ... "We’re proud of our relationship with Bruno Mars, one of the world’s most thrilling and dynamic performers. From his shows at Dolby Live at Park MGM to the new Pinky Ring lounge at Bellagio, Bruno’s brand of entertainment attracts visitors from around the globe. MGM and Bruno's partnership is longstanding and rooted in mutual respect. Any speculation otherwise is completely false; he has no debt with MGM. Together, we are excited to continue creating unforgettable experiences for our guests."

This update comes shortly after a report began circulating this past week that claimed MGM basically owned Bruno over an alleged gambling bill that was worth tens of millions. While Bruno has yet to address the gossip, MGM made it clear that there is nothing shady about their business relationship. BTW, Bruno's got an upcoming residency there at the resort.

Bruno previously opened up to James Corden in 2016 about being a card shark before hitting worldwide fame. In a "Carpool Karaoke" appearance on 'The Late Late Show,' he explained that he used to play poker to help pay his rent in L.A. ... so the dude does like to gamble.