Robert Francis Kennedy Jr. (born January 17, 1954), also known by his initials RFK Jr., is an American environmental lawyer and writer who promotes anti-vaccine misinformation and public health-related conspiracy theories. He is a candidate for the Democratic Party nomination in the 2024 presidential election.

Since 2005, he has promoted the scientifically disproven claim of a causal link between vaccines and autism, and is founder and chairman of Children's Health Defense, an anti-vaccine advocacy group. Since the onset of the COVID-19 pandemic, Kennedy has emerged as a leading proponent of COVID-19 vaccine misinformation in the United States. Much of Kennedy's public health criticisms and writings have targeted prominent figures such as Anthony Fauci, Bill Gates, and Joe Biden. He has written books including The Real Anthony Fauci in 2021 and A Letter to Liberals in 2022.

Kennedy is a son of U.S. attorney general and senator Robert F. Kennedy and nephew of U.S. president John F. Kennedy. After growing up in the Washington, D.C. area and Massachusetts, he graduated from Harvard University and obtained his Juris Doctor degree from the University of Virginia School of Law. Kennedy began his career as an assistant district attorney in New York City. In 1984, he joined Riverkeeper and the Natural Resources Defense Council (NRDC) in 1986, two non-profits focused on environmental protection. He became an adjunct professor of environmental law at Pace University School of Law in 1986. In 1987, he founded the Pace Law School's Environmental Litigation Clinic, where he held the post of supervising attorney and co-director until 2017. He founded the non-profit environmental group Waterkeeper Alliance in 1999, serving as the president of its board