Ian Thomas Garner MacKaye (pronounced /məˈkaɪ/) (born April 16, 1962), is an American singer and guitarist. Active since 1979, MacKaye is best known for being the frontman of the influential hardcore punk band Minor Threat, the post-hardcore bands Embrace and Fugazi, as well as The Evens. He is a co-founder and co-owner of Dischord Records, a Washington, D.C.-based independent record label, along with Jeff Nelson.

A key figure in the development of hardcore punk and an enthusiastic promoter of an independent-minded, do it yourself punk ethic, MacKaye also worked as a recording engineer, and produced releases by 7Seconds, Nation of Ulysses, Bikini Kill, Rites of Spring, Dag Nasty and Rollins Band. Along with his seminal band Minor Threat, he is credited with coining the term "straight edge", though he has stated many times that he did not intend to turn it into a movement.