Rihanna blown away by talented fan at concert

Rihanna was in for a big surprise when she lent her mic to a fan at her concert in Cincinnati on Saturday.

The singer was on her "ANTI" tour, singing "FourFiveSeconds," when she put her mic in the face of fan Terah Stewart.

"'Cause all of my kindness -- " sang Rihanna before she passed the mic to Stewart.

When Stewart belted back, "Is taken for weakness," with his pitch-perfect, powerful voice, both the audience and Rihanna were stunned. The pop star's eyes opened wide as she simultaneously furrowed her brow in shock.

Stewart wrote on Twitter that the moment was unforgettable: "Y'all don't understand how long I have been riding for @rihanna. I will never forget this. She followed me too," he tweeted.

Watch the video below for the moment that threw off RiRi.