The National Cancer Institute (NCI) is the United States Federal Government's principal agency for cancer research and training. The NCI is a component of the National Institutes of Health (NIH), one of eight agencies that compose the Public Health Service (PHS) in the United States Department of Health and Human Services (DHHS). The National Cancer Institute coordinates the National Cancer Program

The United States Congress established the NCI by the National Cancer Institute Act, August 5, 1937, as an independent research institute. Congress then made the NCI an operating division of the National Institutes of Health by the Public Health Service Act, July 1, 1944. Congress amended the Public Health Service Act with The National Cancer Act of 1971 to broaden the scope and responsibilities of the NCI "in order more effectively to carry out the national effort against cancer." Over the years, legislative amendments have maintained the NCI authorities and responsibilities and added new information dissemination mandates as well as a requirement to assess the incorporation of state-of-the-art cancer treatments into clinical practice.