A “toxic workplace” is a colloquial metaphor used to describe a place of work, usually an office environment, that is marked by significant personal conflicts between those who work there. A toxic work environment has a negative impact on an organization's productivity and viability. This type of environment can be detrimental to both the effectiveness of the workplace and the well-being of its employees.

The word toxic was first used as a metaphor for poisonous interpersonal relationships (as opposed to a factual description of a workplace literally involving toxic chemicals) in 1989, in a book about leadership for nurses. This book contrasted a toxic work environment, with a high-conflict and uncollaborative approach, against a "nourishing" workplace, with shared values and active listening.

Toxic work environments may be characterized by horizontal hostility among workers.

Toxic workplaces are created by the actions of toxic employers or employees; that is, individuals who are motivated by personal gain, whether driven by power, money, fame, or special status, utilize unethical means or behaviors to psychologically manipulate, belittle, or frustrate those around them, or divert attention away from their personal inadequate performance or misdeeds. Toxic workers do not feel a sense of duty toward their workplace or their co-workers, especially in regard to ethical or professional conduct toward others. Toxic workers also define relationships with co-workers, not by appropriate organizational structure, but by those who they like/dislike or trust/distrust.

In 2017 and 2021, nineteen percent of Americans suffered abusive conduct at work, according to the Workplace Bullying Institute.

In 2017, the Workplace Bullying Institute found that 61% of bullies were bosses, a figure which rose to 65% in 2021. A 2022 study by McKinsey & Company concluded that women are 41% more likely to be subjected to a toxic workplace culture and that their risk of burnout is elevated.

This phenomenon harms both the company and the employees, including those who are not direct targets. Co-workers are distracted by drama, gossip, and by choosing sides in the ongoing animosity. This can translate into lost productivity. While employees are distracted by this activity, they can not devote time and attention to the achievement of business goals. Positively motivated and ethical employees may try to speak up to a toxic employee, but this can make them a target (see Whistleblower). Managers of toxic employees can feel intimidated by a toxic employee and try to appease the employee in an effort to avoid confrontation. Over time, positively motivated employees drift away from the workplace and may begin to view management as inept and ineffective. This can result in poor job performance as they begin to feel less valued and, therefore, less loyal to the company.

Fellow employees may begin to experience physical symptoms from the stress and worry over whether they or someone they care about in the workplace may be targeted. This can even develop into a clinical depression requiring treatment.