In this chapter we review the research evidence on the relationship between social media use and self-harm. There is much discussion about the possible role of social media in rising rates of self-harm, seen especially in young girls, a discussion that is accompanied by a worry that there may be an associated increased risk of death by suicide. It is beyond the scope of this chapter to go into detail about current understanding of why some people self-harm and some die by suicide - suffice to say that reasons for both are complex and multifactorial. Here we focus specifically on what we know about any potential role of social media and discuss possible mechanisms of action towards harm or benefit in relation to self-harm content.