The entertainers have signed on to climb the continent's highest peak _ Mt. Kilimanjaro, at more than 19,000 feet _ to raise awareness about the need for clean water worldwide.
The Summit on the Summit expedition, set for January, is the brainchild of singer and producer Kenna. His father suffered from waterborne diseases as a child in Ethiopia.
Biel, 27, said she was "astonished" to learn that more than a billion people across the globe have no access to clean water.
"This is a basic human necessity that needs to be addressed now," Biel said in a statement, adding that she's proud to climb Kilimanjaro with the celebrity team "to help any way I can in order to raise awareness toward the life-threatening clean water crisis happening not only in Africa but around the world."
Justin Timberlake _ who's been romantically linked with Biel _ may also be joining the climbers: He told GQ magazine earlier this year that he was preparing for a major mountain climb.
Representatives for the climb declined to comment on the 28-year-old singer's possible participation.
Kenna said more celebrity climbers will be announced in the coming months, and he urges fans to follow the climb online. A donation as small as a dollar can provide 1,000 liters of clean water to those who need it, he said.
"We wanted to make sure there was a way people knew this was an issue and a way for them to do something about it," he said Wednesday. "This is a global issue. It's not an Africa problem. It's not a South America problem. It's a world, global problem. In America, 11 million people go without clean water."