The constitutional right to travel has long been an enigma for courts and academics alike. Despite being widely recognized and regularly applied, relatively little has been written about the breadth or limits of this constitutional guarantee. This gap is particularly striking in the context of restrictive measures designed to curb the spread of a dangerous disease, like quarantines. Although travel rights are directly implicated by such regulations, the law of quarantines (to the limited extent that one has been developed) has almost entirely disregarded the constitutional right to travel. This Article seeks to close this gap by building a detailed model of the Constitution’s protections of movement and travel and then applying this model to quarantines and similar regulations aimed at controlling the spread of a contagious disease. In so doing, this Article makes contributions to the fields of constitutional law and health law, while providing a robust framework of immediate use to policymakers, courts, and litigants responding to the COVID-19 pandemic.