Lester Russel Brown is an American environmental analyst, founder of the Worldwatch Institute, and founder and former president of the Earth Policy Institute, a nonprofit research organization based in Washington, D.C. BBC Radio commentator Peter Day referred to him as "one of the great pioneer environmentalists."

An environmentalist is a person who is concerned with and/or advocates for the protection of the environment. An environmentalist can be considered a supporter of the goals of the environmental movement, "a political and ethical movement that seeks to improve and protect the quality of the natural environment through changes to environmentally harmful human activities". An environmentalist is engaged in or believes in the philosophy of environmentalism or one of the related philosophies.