YouTube, the globally leading video-sharing website and one of the iconic environments of the social media era, has received less attention from language scholars than other social media platforms such as Facebook or Twitter, let alone older communication modes such as discussion forums. One reason for this could be the impression that YouTube is mainly about the moving image, with language playing a peripheral role. In this chapter, we argue that language is a key resource in the semiotic landscape of YouTube. We discuss a number of approaches to its analysis and suggest that researchers have conceptualized the role of language in YouTube in different ways, such as a resource for multimodal semiotic creativity, for digital multi-party interaction, or for participatory discourse on social and political issues. Our discussion is based on a survey of literature as well as on our own research. In the following section, we outline the development and growth of YouTube in the ten years of its existence to date. We then examine YouTube as a complex discourse environment at three levels: the ‘big picture’ of discourse structure and participation framework; the range of multimodal digital recontextualization practices that are often termed ‘remix’; and the realm of audience comments and interaction. We then present two research approaches to language and discourse practices on YouTube, which originate in our own research. The first outlines a social-semiotic and sociolinguistic approach to YouTube as a site for the performance and negotiation of dialect, and the second outlines a corpus-assisted discourse analysis of YouTube as a site of participatory discourse on climate change. We conclude with recommendations for practice and suggestions for future research.