The concept of toxic masculinity is used in academic and media discussions to refer to those aspects of hegemonic masculinity that are socially destructive, such as misogyny, homophobia, and violent domination. These traits are considered "toxic" due in part to their promotion of violence, including sexual assault and domestic violence. Socialization of boys sometimes also normalizes violence, such as in the saying "boys will be boys" about bullying and aggression.

Self-reliance and emotional repression are correlated with increased psychological problems in men such as depression, increased stress, and substance use disorders. Toxic masculine traits are characteristic of the unspoken code of behavior among incarcerated men, where they exist in part as a response to the harsh conditions of prison life.

Other traditionally masculine traits such as devotion to work, pride in excelling at sports, and providing for one's family, are not considered to be "toxic". The concept was originally used by authors associated with the mythopoetic men's movement, such as Shepherd Bliss. These authors contrasted stereotypical notions of masculinity with a "real" or "deep" masculinity, which they said men had lost touch with in modern society. Critics of the term "toxic masculinity" argue that it incorrectly implies that gender-related issues are caused by inherent male traits.

The term "toxic masculinity" originated in the mythopoetic men's movement of the 1980s and 1990s. It later found wide use in both academic and popular writing. Media discussions since the 2010s have used the term to refer to traditional and stereotypical norms of masculinity and manhood. According to the sociologist Michael Flood, these include "expectations that boys and men must be active, aggressive, tough, daring, and dominant".

Some authors associated with the mythopoetic men's movement have referred to the social pressures placed upon men to be violent, competitive, independent, and unfeeling as a "toxic" form of masculinity, in contrast to a "real" or "deep" masculinity that they say men have lost touch within modern society. The academic Shepherd Bliss proposed a return to agrarianism as an alternative to the "potentially toxic masculinity" of the warrior ethic. Sociologist Michael Kimmel writes that Bliss's notion of toxic masculinity can be seen as part of the mythopoetic movement's response to male feelings of powerlessness at a time when the feminist movement was challenging traditional male authority:

Thus Shepherd Bliss, for example, rails against what he calls 'toxic masculinity'—which he believes is responsible for most of the evil in the world—and proclaims the unheralded goodness of the men who fight the fires and till the soil and nurture their families.

In the social sciences, toxic masculinity refers to traditional cultural masculine norms that can be harmful to men, women, and society overall. This concept of toxic masculinity does not condemn men or male attributes, but rather emphasizes the harmful effects of conformity to certain traditional masculine ideal behaviors such as dominance, self-reliance, and competition. Toxic masculinity is thus defined by adherence to traditional male gender roles that consequently stigmatize and limit the emotions boys and men may comfortably express while elevating other emotions such as anger. It is marked by economic, political, and social expectations that men seek and achieve dominance.

In a gender studies context, Raewyn Connell refers to toxic practices that may arise out of what she terms hegemonic masculinity, rather than essential traits. Connell argues that such practices, such as physical violence, may serve to reinforce men's dominance over women in Western societies. She stresses that such practices are a salient feature of hegemonic masculinity, although not always the defining features.