"Adia" is a Sarah McLachlan song that originally appeared on her 1997 album Surfacing. It was co-written by McLachlan and her longtime producer, Pierre Marchand. The song reflected the apology to her best friend for becoming involved with, and later marrying, her friend's ex-partner. "Adia" was the third of four songs from "Surfacing" to be released as a single. It was her most successful US single, peaking at #3 on the Billboard Hot 100. The single, released July 7 1998, contains four tracks: the radio mix of "Adia", the Surfacing mix of "Angel", the original studio version of "I Will Remember You" (as opposed to the live version included on the Mirrorball album, also released as a single), and a live version of "Building a Mystery".
A live version of "Adia" appears on the Mirrorball album.