She was the celebrity face for H&M's swimwear line which gave proceeds to the WaterAid foundation. WaterAid helps deliver clean water and spread hygiene education.
Gyllenhaal went above and beyond for the environment. He's traveled all the way to the Arctic Circle with Salma Hayek to document climate changes. He also shelled out $10,000 to off-set his carbon footprint by planting trees in Mozambique.
The actor/musician was honored with "The Big Help Award" at Nickelodeon's 2011 Kids' Choice Awards for his philanthropic and environmental work.
DiCaprio knows that for some people, going green may be as hard to understand or do as watching Inception. So he's made it simple by offering helpful tips right on his personal website. He also made a documentary on global warming titled The 11th Hour.
The actor made a serious commitment to being eco-friendly, building a home that uses solar power and recycled building materials, conserving shower water,and even traveling to Antarctica to study the effects of warming on the polar region. He also helped launch Global Cool, an organization that teaches people how small, simple steps can help prevent global warming.
It's great to know that Pitt has a heart of gold to go with his charm and good looks. One of his most admirable achievements was establishing the Make It Right Foundation, which helped build eco-friendly homes on the spot where the levee breached in the wake of Hurricane Katrina.
Redford's role as the Sundance Kid has become the namesake for his dedication to saving the planet. He founded the Sundance Preserve nearly 40 years ago, and has since spawned a festival, channel and a resort, all dedicated to conservation and preservation.
Portman is both a vegan and big-time supporter of animal rights. The Harvard graduate trekked through Rwanda's rainforest to learn about the endangered mountain gorilla for a special Animal Planet documentary. She also took veganism to the runway, introducing a line of clothes for Té Casan composed of all man-made materials.
Diaz is making sure her Hollywood lifestyle doesn't leave a big carbon footprint. The bubbly star drives a Prius and sticks to the basic reduce, reuse, and recycle credo.
As an EMA Young Hollywood Board member, the Entourage actress has mentored kids at local L.A. schools by helping plant and improve organic gardens.
The country crooner has become one of the fathers of the alternative fuel movement, thus earning him the nickname BioWillie. He started producing and distributing biodiesal in 2004.
MORE PHOTOS: Stars in eco-friendly cars