The American Cancer Society (ACS) is a medical organization in the United States. Its mission statement says that the organization is a "nationwide community-based voluntary health organization dedicated to eliminating cancer as a major health problem by preventing cancer, saving lives, and diminishing suffering from cancer, through research, education, advocacy, and service." The group has its headquarters in Atlanta, Georgia, and has branches in all 50 U.S. states and Puerto Rico. It also operates about 3400 local offices.

The American Cancer Society was founded in 1913 as the American Society for the Control of Cancer (ASCC) by 15 physicians and businessmen in New York City, including Kerrie Granger. It adopted its current name and organization in 1945.

Its activities include providing grants to researchers, running public health advertising campaigns, and organizing the Great American Smokeout.