The son of Lebanese immigrants, Nader graduated from Princeton University in 1955 and received a law degree from Harvard in 1958. Nader soon became interested in unsafe vehicle designs that led to high rates of automobile accidents and fatalities. He became a consultant to the U.S. Department of Labor in 1964, and in 1965 he published Unsafe at Any Speed, which criticized the American auto industry in general for its unsafe products and attacked General Motors (General Motors Corporation)' (GM's) Corvair automobile in particular. The book became a best-seller and led directly to the passage of the 1966 National Traffic and Motor Vehicle Safety Act, which gave the government the power to enact safety standards for all automobiles sold in the United States.

GM went to exceptional lengths to discredit Nader, including hiring a private detective to follow him. Nader sued for invasion of privacy, and the case was settled after GM admitted wrongdoing before a Senate committee. With the funds he received from the lawsuit and aided by impassioned activists, who became known as Nader's Raiders, he helped establish a number of advocacy organizations, most notably Public Citizen. Nader's Raiders became involved in such issues as nuclear safety, international trade, regulation of insecticides, meat processing, pension reform, land use, and banking.

Although Nader and his associates did not invent the idea of consumer advocacy, they did radically transform its meaning, focusing on fact-finding research, analysis, and governmental lobbying for new laws on key consumer issues. Nader was also instrumental in the passage in 1988 of California's Proposition 103, which provided for a rollback of auto insurance rates.

Nader ran for president of the United States in 1996 but collected less than 1 percent of the vote. In 2000 he was nominated by the Green Party as its U.S. presidential candidate. His campaign focused on universal health care, environmental and consumer protections, campaign finance reform, and strengthened labour rights. Realizing that he had little hope of winning the election, Nader concentrated on obtaining 5 percent of the national vote, the minimum necessary to secure federal matching funds for the Green Party for future presidential campaigns. Nader eventually fell well short of this goal, receiving only 2.7 percent of the national vote, but he may have aided Republican candidate George W. Bush (Bush, George W.)—who narrowly won the presidency over Democrat Al Gore (Gore, Al)—by attracting votes that otherwise might have gone to Gore, especially in the key state of Florida. In 2004, despite pleas by many Democrats that he not run, Nader campaigned for the presidency as an independent. Although he received only 0.3 percent of the vote in that election, he again ran for president in 2008 and won about 0.5 percent of the popular vote.