This chapter presents a model of social media engagement. The model’s components–presentation of self, action and participation, uses and gratifications, positive experiences, usage and activity counts, and social context–are discussed in depth with relevant evidence and examples. The model supports the main thrust of the chapter to combine tangible, e.g., usage and activity counts, and more abstract, e.g., positive user experiences, indicators of engagement in order to better understand why people engage with social media, the extent to which they engage, what social media platforms they interact with, and the outcomes of their engagement. The chapter includes illustrative case studies and concludes with some thought-provoking questions to guide future research, including the ethical and social implications of social media engagement