Ian Thomas Garner MacKaye (; born April 16, 1962) is an American musician. Active since 1979, he is best known as the co-founder and owner of Dischord Records, a Washington, D.C.-based independent record label and the frontman of hardcore punk band Minor Threat and post-hardcore band Fugazi. MacKaye was also the frontman for the short-lived bands the Teen Idles, Embrace, and Pailhead, a collaboration with the band Ministry. MacKaye is a member of The Evens, a two-piece indie rock group he formed with his wife Amy Farina in 2001 and in 2018 formed the band Coriky with Farina and his Fugazi band mate Joe Lally.

Along with his seminal band Minor Threat, he is credited with coining the term "straight edge" to describe a personal philosophy that promotes abstinence from alcohol and other drugs, though MacKaye has stated that he did not intend to turn it into a movement.

A key figure in the development of hardcore punk and an independent-minded, do-it-yourself punk ethic, MacKaye has produced releases by Q and Not U, John Frusciante, 7 Seconds, Nation of Ulysses, Bikini Kill, Rites of Spring, Dag Nasty and Rollins Band.