ABSTRACT This study examines aggression between rival football fans, focusing on the role of ethnicity and urban identity. It surveyed 302 fans from Rasht and Bandar Anzali in Guilan province, Iran. The findings revealed a statistically significant positive correlation between a favorable attitude toward aggression against rival fans and three key factors: ethnic/urban identity (correlation coefficient: 0.409), ingroup love (correlation coefficient: 0.355), and outgroup hatred (correlation coefficient: 0.407). The collective explanatory power of ethnic/urban identity, outgroup hatred, and ingroup love accounted for 39% of the variance in the favorable attitude towards aggression against rival fans. Ethnic/urban identity levels demonstrated predictive power, accounting for 15% of the variance in outgroup hatred and 13% in ingroup love. This research illuminates the intricate dynamics of fan aggression, highlighting the nuanced roles of identity and emotions within sports fandom. The findings contribute valuable insights that inform future studies and interventions to understand and mitigate aggression in sports-related contexts.