Based on an in-depth literature review, this paper explores the terms ‘radicalisation’, ‘de-radicalisation’ and ‘counter-radicalisation’ and the discourses surrounding them. Much of the literature on radicalisation focuses on Islamist extremism and jihadist terrorism. This is also reflected in this Research Paper which explores the relationship between radicalisation, extremism and terrorism. Historically, ‘radicalism’ – contrary to ‘extremism’ – does not necessarily have negative connotations, nor is it a synonym for terrorism. Schmid argues that both extremism and radicalism can only be properly assessed in relation to what is mainstream political thought in a given period. The paper further explores what we know well and what we know less well about radicalisation. It proposes to explore radicalisation not only on the micro-level of ‘vulnerable individuals’ but also on the meso-level of the ‘radical milieu’ and the macro-level of ‘radicalising public opinion and political parties’. The author reconceptualises radicalisation as a process that can occur on both sides of conflict dyads and challenges several widespread assumptions. The final section examines various counter-radicalisation and deradicalisation programmes. It concludes with a series of policy recommendations.