Public pensions require fundamental reform, but defenders of the current system have advanced arguments that do not reflect sound economic thinking. These public-pension fallacies endure in political debates, even as finance economists have roundly rejected them. This backgrounder addresses nine of the most common fallacies promulgated by defenders of public pensions-everything from the belief that governments can ignore investment risk to the idea that major "transition costs" prevent reform-and concisely explains why economists find each argument so unpersuasive. Correcting these fallacies will improve public discourse on the pension issue and remove an impediment to reform.