Stephen Joel Barrett is an American retired psychiatrist, author, co-founder of the National Council Against Health Fraud (NCAHF), and the webmaster of Quackwatch. He runs a number of websites dealing with quackery and health fraud. He focuses on consumer protection, medical ethics, and scientific skepticism.

Quackwatch is a United States-based website, self-described as a "network of people" founded by Stephen Barrett, which aims to "combat health-related frauds, myths, fads, fallacies, and misconduct" and to focus on "quackery-related information that is difficult or impossible to get elsewhere". Since 1996 it has operated the alternative medicine watchdog website quackwatch.org, which advises the public on unproven or ineffective alternative medical remedies. The site contains articles and other information criticizing many forms of alternative medicine.