Rihanna was left shocked after a fan upstaged her with an incredible vocal performance at a gig in Cincinnati, Ohio.

The Work singer was performing her song FourFiveSeconds at the city's U.S. Bank Arena on Saturday (19Mar16) when she offered the microphone to Terah Jeh, a fan in the front row of the audience.

Terah, who according to TMZ.com has performed in choirs as an amateur singer, then belted out the next line of the track so perfectly that the Barbadian star was seen looking on in shock.

Rihanna shared a video clip of her fan's moment in the spotlight on Instagram, captioning the footage, "Wow, he can sing!"

According to Terah, the star is even looking to keep in contact with him by following him on Twitter after his amazing vocal intervention, writing, "Y'all don't understand how long I have been riding for @rihanna, I will never forget this. She followed me too."

The video of the tuneful fan was widely shared on social media, and with Teraj writing that the attention had given him, "a whirlwind 24 hours" since his star turn alongside his musical idol.

Professing his affection for the star he added, "Seriously @rihanna, I love you. Endlessly."

Rihanna's ANTI world tour, which has seen a number of dates rescheduled due to production difficulties, continues on Tuesday (22Mar16) with a date in Washington D.C.