Stars flocked to Manchester, England Sunday night ... for the annual event -- including Shawn Mendes who belted out a couple songs onstage at the newly opened Co-op Live.

Rita Ora handled hosting duties for the evening stunning in a futuristic outfit that showed off a ton of skin ... including her tight midriff. And, Jodie Turner-Smith presented an award in a low-cut, black dress.

"Beautiful Things" singer Benson Boone stunned the audience with his show -- hopping atop a tall platform and belting out some impressive notes in an angelic all-white outfit.

Among the other stars in attendance ... Tyla, Busta Rhymes, LL Cool J, Peso Pluma, Teddy Swims, Aaron Taylor-Johnson, Gavin Rossdale and many more bold-faced names.

While they're technically called the European Music Awards, a ton of American artists -- from Taylor Swift and Ariana Grande to Sabrina Carpenter and Billie Eilish are up for trophies at the ceremony.