Cyberbullying in romantic relationships—also called electronic dating aggression (EDA) or cyber dating abuse and harassment—occurs throughout adolescence and emerging/young adulthood. Some proportion of youth in middle school, high school, and college each report perpetrating and/or being the victim of EDA. Yet each developmental stage might represent variation in the nature of electronic dating abuse experiences and its consequences for youth. Transition to middle school and early adolescence represents a time characterized by change, and the start of engagement in romantic relationships for many. It may mark a time when youth are particularly vulnerable to abusive relationships, including EDA. Transition to college and emerging adulthood similarly represents a time characterized by change, and the start of living away from home for many young people. Peer groups—and sometimes romantic partners—replace the family of origin in daily living arrangements. Like early adolescence, this may mark a time when these emerging adults are particular vulnerable to cyber dating abuse. This chapter will explore EDA across developmental stages of adolescence and young adulthood, and will examine current understandings of such abuse at each stage based on prevalence, risk factors for abuse, and consequences of it.