In this chapter, we present and discuss the concept of bullying and harassment at work as it has developed since the late 1980s and early 1990s in what we could call the ‘European tradition’ in workplace bullying research, and from which other perspectives on bullying elsewhere have originated. We start by looking at the development and increasing prominence of the bullying concept in European countries and around the globe. The various key defining characteristics of the phenomenon are then presented, elaborated and discussed, such as frequency, duration or longevity, power-imbalance, status or position of bullies and victims, objective and subjective bullying, and interpersonal as opposed to organizational bullying. We further discuss if bullying is a concept of its own or to be seen as a mere sub-concept of aggression or interpersonal conflicts, arguing strongly for the former view. The chapter then discusses the conceptual models of bullying that have so far dominated European research on workplace bullying.