Online curricula can make high-quality health professions education accessible in virtually any setting. They can enhance teaching and learning by both standardizing curricular resources and individualizing curricular experiences. Despite growing demand for and institutional interest in online curricula for medical education, many medical educators lack a framework for online curriculum development. Without rigorous and thoughtful development, online curricula can waste opportunity and resources by leading to education that is inferior to traditional methods. In this article, the authors describe a systematic approach to online curriculum development based on the Six-Step Approach for Curriculum Development for Medical Education, a widely used method that has led to successful implementation of a variety of traditional and online curricula. In each step, special considerations for curricula with larger and more diverse learner audiences-characteristic of many online curricula-are highlighted. Four common online curricular formats are also discussed: blended curricula, instructor-led fully online curricula, self-paced modules, and massive open online courses (MOOCs). The authors emphasize factors that differentiate one online format from another, including the budgetary, technical, and human resource requirements for each. The article concludes by urging medical educators to pursue opportunities to study and disseminate online curricular work.