Hounsou, who was born in Benin, West Africa, and Davis are backing Oxfam America's latest famine campaign to help people in the Sahel region.
Both stars have set up their own online fundraising pages in the hope of generating $10,000 each.
The Blood Diamond actor explains, "I have seen the difference that aid programs and organisations like Oxfam make on a daily basis around the world.
"It is our duty to help those in need, and I'm asking you to do your part as a fellow member of the human race."
In a post on her own page, Davis writes, "Right now a food crisis is gripping the Sahel region of West Africa. And it's not making it to the headlines. Please help me support Oxfam's lifesaving work in this region where more than 18 million people are at risk. Donate to my page, or better yet, start your own."