Right-wing terrorism has changed its face. Gone are the days of structured cells and hierarchical command chains. Today’s threat is the “lone wolf” extremist—radicalised online, socially isolated, and driven by a blend of identity crisis, conspiracy thinking, and a deep-seated resentment toward political and media elites. This book investigates the rise of far-right lone actors as a new, transnational security challenge. Drawing on recent cases from Europe and North America, it explores how digital subcultures, algorithmic echo chambers, and cultural narratives of victimhood transform individuals into ticking time bombs. The “phantom” quality of this threat lies in its elusiveness: lone attackers often act without prior warning, outside of known extremist networks, yet consume and echo the same ideological patterns—from xenophobic great replacement myths to anti-government sentiment. Florian Hartleb argues that conventional counter-terrorism tools fail to grasp the psychological and symbolic logic of these actors, who seek fame, martyrdom, or revenge rather than strategic gain. By combining insights from political science, psychology, and digital sociology, The Far-Right Phantom highlights the urgent need for new prevention models—ones that bridge the gap between online monitoring, civic education, and early psychological intervention. At stake is not only public safety, but also the resilience of open societies under pressure from an enemy that hides in plain sight: the radicalised individual next door.