Dylan Klebold, American student and murderer (b. 1981)
Eric David Harris (April 9, 1981 – April 20, 1999) and Dylan Bennet Klebold (; September 11, 1981 – April 20, 1999) were an American mass murder duo who perpetrated the Columbine High School massacre on April 20, 1999. Harris and Klebold killed 13 people and wounded 24 others, at Columbine High School, where they were seniors, in Columbine, Colorado, United States. After killing most of their victims in the school's library, they later committed suicide. At the time, it was the deadliest high school shooting in U.S. history, with the ensuing media frenzy and moral panic leading it to become one of the most infamous mass shootings ever perpetrated.

Harris and Klebold were both born in 1981. Harris was born in Wichita, Kansas, but moved around frequently as a child due to his father's occupation in the United States Air Force, while Klebold was born and raised near Columbine. Harris' family eventually settled in Colorado. Shortly after, Harris and Klebold met, while they were in the 7th grade. Over time, they became increasingly close. By the time they were juniors, they were described as inseparable. There are differing reports; some say Harris and Klebold were very unpopular students once they were upperclassmen, and frequent targets of bullying, while others say they were not near the bottom of the school's social hierarchy and each had many friends. From their journals, Harris and Klebold had seemed to begin planning the attack by May 1998, nearly an entire year before the attack. Throughout the next 11 months, Harris and Klebold meticulously built explosives and gathered an arsenal of weapons. Both Harris and Klebold each left behind several journal writings and home videos, ones they made both alone and together, foreshadowing the massacre and explaining their motives. Harris and Klebold hoped this content would be viewed by the public extensively, although much of the evidence has never been released by authorities.

After the massacre, it was widely believed Harris and Klebold were part of a clique in school called the "Trenchcoat Mafia", a group of misfits in the school who supposedly rebelled against the popular students. This turned out to be untrue, as neither Harris nor Klebold had any affiliation with the group. The pair's aforementioned writings and videos gave insight into their rationale for the shooting. The FBI concluded that Harris was a psychopath, who exhibited a lack of empathy, narcissistic traits and unconstrained aggression. Klebold, however, was concluded to be an angry depressive, who showed low self-esteem, anxiousness and a vengeful attitude toward individuals who he believed had mistreated him. However, neither Harris nor Klebold were formally diagnosed with any mental illnesses prior to the attack. In the following years, various media outlets attributed multiple motivating factors to the attack, including bullying, mental illness, racism, psychiatric medication and media violence. Despite these conclusions, the exact motive for the attack remains inconclusive.

Harris and Klebold have become pop culture icons, with the pair often portrayed, referenced and seen in film, television, video games, music and books. Many killers since the shooting have taken inspiration from the pair, either hailing them as heroes, martyrs and gods, or expressing sympathy for the pair. Harris and Klebold also have a fanbase, who have coined the term "Columbiners", who write fan fiction and draw fan art of them. Others have also dressed as the duo for cosplay or Halloween.