This chapter outlines the brief definitions of aggression and violence and their subtypes. Conceptions and misconceptions regarding the association of mental illness with aggression and violence are considered in three major mental illnesses: schizophrenia, personality disorders and autism. The chapter highlights the key neurobiological features that are putatively linked with the propensity to commit acts of violence and aggression. It examines whether the presence of additional, comorbid disorders aggravates the risk for violence and aggression. The chapter discusses some common underlying psychological and neurobiological causes, highlighting the social brain network as a possible neuro‐biological framework to understanding violence and aggression in these disorders. The overlap between brain networks implicated in aggression and the processing of socio‐cognitive abilities suggest that pathological aggression can be conceptualized as a disorder of the social brain. Aggression and antisocial behavior are a likely consequence of mental illnesses affecting the social brain.