The term „Incel” describes a heterogeneous group of predominantly young men who meet and organize themselves in various online spaces of the so-called manosphere. In recent years, Incels have increasingly become the subject of media as well as political and scientific attention. Reasons for this are a.) the openly articulated hatred of women and b.) several attacks that had been perpetrated by selfdefined Incels or right-wing extremist men who share ideological grounds with Incels or who have radicalized themselves in their online spaces on the other hand. This article provides an introduction to the basic terminology and ideology of Incels, traces processes of online radicalization, outlines overlaps with other forms of extremism, and analyzes potential paths of prevention and intervention.