This chapter studies the relationship between free speech and commercial advertising. In the contemporary world, a substantial percentage of the universe of public communication consists of advertising. Speech offering to sell goods and services, typically with inducements to purchase, and often including the price and other conditions of the proposed sale, is a ubiquitous part of modern life. An important question in the theory and practice of freedom of speech is the extent to which, if at all, such communications should be protected against government regulation. Given that the United States is something of a protective outlier on free speech questions generally, even when compared to other liberal industrialized democracies, it is not surprising that free speech protection for commercial advertising is more robust in American law than it is anywhere else in the world. But the question has arisen in many other countries that profess to take the freedom of speech seriously, and thus the chapter will deal with the question of free speech protection for commercial advertising of some sort and to some degree as a question with worldwide implications, and with both theoretical and doctrinal dimensions. It is common in much of the relevant literature to refer to the topic under discussion as ‘commercial speech’.