Markets increasingly use and create networks, both social and technological. Some examples: the complex trading networks that underlie modern financial markets and supply chains; social media platforms; dating apps. These profoundly affect the economy and society more broadly: financial interdependencies are critical in economic crises, while rumors on Twitter have come to play a central role in our politics. How can we make sense of these phenomena—as individuals, within companies, and as policymakers? This seminar teaches models from the economics and statistics of networks that are essential to the task. Topics include the network origins of recessions, the diffusion of information and rumors, racial segregation, and matching markets. We emphasize how network models relate to key ideas from microeconomics.