100th Window is the fourth studio album by English electronic music group Massive Attack, released on 10 February 2003 by Virgin Records.

100th Window features vocals from regular guest Horace Andy, as well as newcomers Sinéad O'Connor and Damon Albarn (performing as 2D from Gorillaz).

Del Naja initially conceived of 100th Window in its untitled form in early 2000 at the Christchurch Studios in Clifton, Bristol, recruiting Lupine Howl, a band made up of ex-members of Spiritualized, for the new project.

In a November 2001 interview, Lupine Howl's lead singer Sean Cook described the sessions as "very experimental [...] minimal loops and noises that were fed to our headphones from the computer up in the control room.

However, in a post to Massive Attack's forums in July 2002, Del Naja subsequently announced that the band had become "very unhappy with the shapes being formed", and that by the beginning of 2002 they had discarded most of the material that was written up to that point; the September 11 attacks also motivated him to depart from the original tone of the album.