Straight edge is a subculture of hardcore punk whose adherents refrain from using alcohol, tobacco, and recreational drugs, in reaction to the excesses of the punk scene. It began in the late 1970s and early 1980s and was partly characterized by shouted rather than sung vocals. Straight edge individuals of this early era often associated with the original punk ideals such as individualism, disdain for work and school, and live-for-the-moment attitudes. The movement was influenced by the political and social climate of its origin, around the time of the "Just Say No" campaign and a rise in conservative viewpoints.

Straight edge individuals abstain from alcohol, tobacco, illicit drugs, and "promiscuous" sex. While straight edge holds different meanings to many different people, a lifetime commitment to abstaining from drugs, tobacco, and alcohol remains the cornerstone of the movement. Many also speak out against "conquest" sex, or using others for temporary gratification. Beyond these basic principles, adherents have blended straight edge with other lifestyles and ideologies. Many adopt vegetarian or vegan diets. Some avoid caffeine.

The letter X is the most known symbol of straight edge, and it sometimes is worn as a marking on the back of both hands, and it can be displayed on other body parts as well. Some followers of straight edge put the symbol on clothing and pins, and many bands aligned with the culture incorporate it into their names.

Despite the changing representations of straight edge and its movement into the mainstream, the core values of it - abstaining from drinking, smoking, and drugs - remain unchanged from when the movement first gained traction. For some, being straight edge is still a definitive and unwavering lifelong commitment.