Kellan Lutz, Britney Spears, Hayden Panettiere and more celebs are teaming up for charity.

The trio and 10 other celebrities are cleaning out their closets for a cause, signing and contributing a pair of jeans each for Blue Jeans Go Green's "Great Denim Challenge."

The star-studded auction is designed to raise awareness about textile recycling and help the program collect its one-millionth piece of denim.