Shannon Noll has apologised after a video capturing a foul-mouthed rant in which he threatened to punch a concertgoer went viral over the weekend.

The singer had been performing at the Duck Creek Picnic Races in Nyngan in regional NSW on Saturday, when he interrupted his set to call out a "f---head" in the crowd who had thrown a beer can onstage.

"Come on then, that f---head in the tie. You're a f---ing maggot. Have some f---ing balls to come up here instead of throwing something from there... Come on, cheapshot prick," Noll yelled at the concertgoer, as his band continued playing the opening strains of Daryl Braithwaite's The Horses.

The almost two-minute rant continued with Noll inciting the crowd to "shame that motherf---er there" and offering $100 for someone to "punch that f--- for me".