The Sierra Club Foundation is an American nonprofit charitable organization focused on environmental efforts. It is an independent 501(c)(3) social welfare organization, the fiscal sponsor of the charitable programs of the Sierra Club. The organization's stated mission is to "help educate, inspire, and empower humanity to preserve the natural and human environment."

The Sierra Club is an American environmental organization with chapters in all 50 U.S. states, Washington D.C., and Puerto Rico. The club was founded in 1892, in San Francisco, by preservationist John Muir. A product of the progressive movement, it was one of the first large-scale environmental preservation organizations in the world. Since the 1950s, it has lobbied politicians to promote environmentalist policies, even if they are controversial. Recent goals include promoting sustainable energy and mitigating global warming, as well as opposing the use of coal, hydropower, and nuclear power. Its political endorsements generally favor liberal and progressive candidates in elections.