Illegal fishing, also called pirate fishing, occurs on an industrial scale and has global consequences. Outlaw vessels deplete fish stocks, harming communities that rely on fish for food and economic security. Illegal fishing also threatens fragile marine ecosystems. Illegal operators employ a variety of techniques to avoid detection while bending and breaking regulations. To end illegal fishing, we need a global requirement that fishing vessels have unique identification numbers (known as IMO numbers); ratification of the United Nations' Port State Measures Agreement; and improved information sharing among national law enforcement agencies. Each of these components will improve monitoring and enforcement of fisheries crimes.