This chapter examines the concept of autonomy in American constitutional law as it applies to the freedom of individuals and some private associations to make certain important choices without undue intervention from the government. It first traces the origins of the understanding of autonomy as personal freedom before turning to the autonomy principle found in Supreme Court decisions applying the Constitution’s First and Fourteenth Amendments, with occasional references in the jurisprudence of the Second, Fourth, Fifth, and Sixth Amendments. It then analyzes the tension between personal autonomy to waive constitutional protections (e.g., the Fifth Amendment right against self-incrimination) and the government’s legitimate role in encouraging autonomous actions. It also considers autonomy in relation to what the Court has called the “personal” realm, which involves matters of privacy, family life, sexual relations, reproduction, education, self-defense within the criminal justice system, religious belief and practice, and freedom of thought and speech.