Trademark and related unfair competition laws promote fair competition and protect goodwill but do not do so by providing broad monopoly rights. Instead, rights to a particular mark are limited to leave room for competitors, the dissemination of information, and the production of creative expression and commentary. This latitude is protected in part by limits on the scope of the rights afforded, but also by defenses to these claims. This chapter primarily considers affirmative defenses to trademark infringement, trademark dilution, and false endorsement claims, focusing on defenses that serve the goals of free expression and fair competition. These free-speech-based defenses should be of particular interest to comparative law scholars and non-US practitioners because of their unique and elevated status in US law. The First Amendment to the US Constitution expressly prohibits Congress (and by extension states) from making or enforcing laws that “abridg[e] the freedom of speech.” This foundational aspect of US law has influenced the development of and the interpretation of speech-based defenses to trademark and related claims.1