This monograph is a call to action. It is an urgent request to those using the web to help find solutions to problems facing healthcare globally. The disciplines of Web Science and its subfield Health Web Science explore how the World Wide Web drives discussions, technologies, policies, and solutions, which surround health issues. The monograph presents Health Web Science as a sub-discipline of Web Science that, while being concerned with the Web's impact on health and wellbeing, also examines the impact of the Web's health-related uses on the design, structure, and evolution of the Web itself. Understanding and appreciating the overlapping, yet divergent disciplinary orientation of Health Web Science compared to related research domains, motivates specific research efforts around better utilization of, innovation on, and communication over and within the Web. Foundations and Trends in Health Web Science is an ideal reference for researchers and practitioners with an interest in this emerging topic.