This focus section on extremism, radicalization, and sexual aggression presents recent research from two currently important fields of aggression research. It presents five papers that were presented at the Workshop on Aggression at the Psychologische Hochschule Berlin in 2018. The first three address risk factors for radicalization and acceptance of group-related aggressive behavior, namely hate speech against Muslims and collective violent behavior towards perceived out-groups including Jews and Ukrainians. The last two studies address sexual aggression: one examines the prevalence and risk factors for sexual victimization among a large student population in Chile; the other considers risk factors for potential sexual aggression in a Germ...