Workplace bullying, like childhood bullying, is the tendency of individuals or groups to use persistent aggressive or unreasonable behavior against a co-worker or subordinate. Workplace bullying can include such tactics as verbal, nonverbal, psychological, physical abuse and humiliation. This type of aggression is particularly difficult because, unlike the typical forms of school bullying, workplace bullies often operate within the established rules and policies of their organization and their society. Bullying in the workplace is in the majority of cases reported as having been perpetrated by management and takes a wide variety of forms. Bullying can be covert or overt.

While there is no single formal definition of workplace bullying, several researchers have endeavoured to define it. Some categorize all harmful boss-behaviour and actions of malintent directed at employees as bullying. Bullying behaviours may be couched in humiliation and hazing rites and iterative programs or protocols framed as being in the best interests of employee development and coaching. Others separate behaviours into different patterns, labeling a subset of those behaviours as bullying, explaining that there are different ways to deal effectively with specific patterns of behaviour. Some workplace bullying is defined as involving an employee's immediate supervisor, manager or boss in conjunction with other employees as complicit, while other workplace bullying is defined as involving only an employee’s immediate supervisor, manager or boss.

Gary Namie is social psychologist and anti-workplace bullying activist from Bellingham, Washington. He is the director of the Workplace Bullying Institute.

Namie launched a national campaign against workplace bullying in Benicia, California in 1997 with his wife Ruth, who has a doctorate in clinical psychology, after she was subject to harassment at work. Namie has an AB from Washington & Jefferson College in Washington, Pennsylvania, and an MA in Research Psychology from San Francisco State University and a PhD in social psychology from the University of California, Santa Barbara in 1982. Namie taught psychology and management at US colleges for two decades. He taught the first university course in the US on workplace bullying. He was also a corporate manager for two regional hospital systems. He was the expert witness in the nation's first "bullying trial" in Indiana with the verdict upheld by the state Supreme Court.^{[citation needed]}

In 2007 and 2010 the Workplace Bullying Institute commissioned Zogby International to conduct the representative surveys of all adult Americans on the topic of workplace bullying. The survey reported that 1/3 of American workers have experienced workplace bullying. The Namies lobbied for a "Healthy Workplace Bill" sponsored by Kelli Linville to give employees the right to sue if harmed by an abusive workplace.