From the USO to PETA, it's become common practice for celebrities to leverage their superstar status in favor of the charities and issues dear to their hearts.
SheKnows salutes the Top 10 Celebrity Activists—and the causes that move them:
U2's frontrunner has a passionate concern for the global issues of poverty and AIDS awareness, which led to the foundation of the celebrity-endorsed, nonpartisan organization ONE.
The feisty star of "Thelma & Louise" has publicly supported many liberal causes and organizations. She caused a stir at the 2003 Oscars when she made the peace sign on camera in the wake of the recent Iraq invasion.
The talk show superstar has founded several charitable organizations and in 2007 she was awarded The Elie Wiesel Foundation for Humanity Humanitarian Award for her global humanitarian efforts.
She may be a looker, but Jolie's eyes are often on humanitarian missions as Goodwill Ambassador to the United Nations High Commissioner for Refugees. The Church World Service Immigration and Refugee Program honored her with their Humanitarian Award.
The Oscar winning actor also owns his own product line called "Newman's Own," which offers salad dressings, pasta sauces and other treats. He and the Newman's Own Foundation have donated approximately $200 million to various charities.
Box office heartthrob Clooney spent five days in Darfur in 2006 where he opposed genocide and made a plea to the U.S. and NATO to do more to help. Later that year he made a star appearance before the UN Security Council and pleaded the cause before the U.S. Congress.
"Cheers" to vegan Woody Harrelson as an outspoken environmentalist who has criticized big oil and advocates the legalization of hemp. He has been arrested several times for his public protests.
17-year-old Kilcher made an environmental statement by leasing the Honda FCX Hydrogen Fuel Cell Vehicle. For Kilcher, it seems, "The New World" she envisions includes cleaner air and bluer skies.
Michael J. Fox
Beloved actor Michael J. Fox earned a spot on the TIME 100 List for his work as a Parkinson's activist. In 1999 he spoke out about the disease on Capital Hill.
Known for his brooding style and diversity of roles, Penn has openly criticized the Bush administration. He has gone so far as to take out a $56,000 open advertisement spurring their policies in the Washington Post. The star has made appearances in such hot spots as post-Katrina New Orleans, Iraq and Iran.