Two is better than one, especially when the duo are as in sync as Rihanna and Eminem, who make hits every time they get together (i.e., "Monster," "Love the Way You Lie"). And now, they'll be heading on tour together. But they aren't the only stars who've linked up to bring a blockbuster bill to a stadium near you. Check out these other unforgettable co-headling tours.
(Photos from left: Stefan Gosatti/Getty Images, Frederick M. Brown/Getty Images)