Eminem was joined by a special guest during his headlining set at Lollapalooza last night (August 1).

40 minutes into the Slim Shady star’s show Rihanna appeared on stage for a couple of duets ahead of the pair’s joint ‘The Monster’ tour which kicks off on August 7.

Eminem and Rihanna treated the Chicago crowd to renditions of their No. 1 hits ‘Love The Way You Lie’, and ‘The Monster’. Rihanna also filled in for Dido to deliver the chorus on ‘Stan’.

The rest of the Detroit rapper’s set was made up by many of his biggest hits with ‘Not Afraid’ and ‘Lose Yourself’ serving as his closing numbers.

Eminem and Rihanna will play the following dates on their ‘The Monster’ tour:

August 7 - Los Angeles Rose Bowl

August 8 - Los Angeles Rose Bowl

August 16 - New York Metlife Stadium

August 22 - Detroit Comerica Park

August 23 - Detroit Comerica Park

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Watch Eminem and Rihanna live at Lollapalooza below: