Google, Apple, Amazon, Meta, and most recently Visa have all been sued by the government in recent years for monopolizing sectors of the American economy. What does it mean for a company to become a monopoly? Why should we care? In this class, we will do a deep dive into monopolies: how they come about, how they affect the economy, and how our nation's laws check them. We will start with a brief history lesson on the robber barons of the late 19th century and the emergence of antitrust laws. Then, we will go through the elementary basics of how economists today model the effects of monopolies on markets--things like supply, price, and quantity. Finally, we will discuss hot topics and current events in antitrust law and policy.