Humans and the effects of their activities now substantially influence the entire planet, including its oceans, climate, atmosphere, and lands. Human influence has become so large that earth scientists have debated whether to identify a new geologic time period: the Anthropocene. The Anthropocene will surely have substantial effects on society and economies, and law will be no exception. The Anthropocene is the product of the aggregation of billions of individual human actions, the impact of which is exponentially increasing because of growing technological advances and population. Humans will inevitably respond to the Anthropocene, if only to adapt to the significant changes in oceans, climate, biodiversity, and other critical functions upon which society depends. These responses will ineluctably lead to greater government involvement in a wide range of human activities and the constant updating of government laws and regulations to respond to new challenges. The result will put pressure on a wide range of legal doctrines in public and private law, including torts, property, constitutional, administrative, and criminal law. These changes will parallel similar revolutionary legal changes associated with industrialization and the development of a national economy in the United States in the nineteenth and twentieth centuries. Just as with those legal changes, the legal changes of the Anthropocene will put pressure on normative commitments at the heart of American law, including the classical liberal paradigm that government intrusion into individual action should be the exception, rather than the norm. Managing the impacts of these legal changes will be a key challenge for the legal system in the next century.