This literature review examines the radicalisation of men within the involuntary celibate (Incel) community, a subgroup of the broader manosphere: online men’s resistance movements against feminism and female empowerment. The incel ideology, shaped by perceptions of victimhood, fatalism, and biological determinism, fosters toxic narratives that have, in some cases, led to gender-based violence. The internet plays a critical role in facilitating incel radicalisation, providing spaces where harmful beliefs are reinforced. While most incels are not violent, the potential for extremism remains a significant concern. This chapter reviews the historical underpinnings of the incel movement, the characteristics associated with incel identity, and conceptualisations of incel ideology-fuelled violence. Drawing on wider radicalisation literature, theoretical models of radicalisation and strategies for de-radicalisation and prevention are discussed.