Sigil (/ˈsɪɡɪl/ SIG-il) is a fictional city and the center of the Planescape campaign setting,[2] for the Dungeons & Dragons fantasy role-playing game.

According to Steve Winter in 30 Years of Adventure: A Celebration of Dungeons & Dragons, "a movable base, like a vessel of some sort (or an artifact, which was the original idea for the means of traversing the planes) wouldn't do it.

[3] Sigil's fifteen factions were created because "Vampire: The Masquerade was a particularly hot game at [the] time and one of the ideas in it that we really liked was the clans.

Jim Ward wanted to be sure that players had something to identify with and to give them a sense of belonging in this alien venue [Sigil]".

Shannon Appelcline, author of Designers & Dragons, commented that while Sigil "had been largely ignored during the 3e era", it "was faring better in 4e, despite the large-scale restructuring of D&D's cosmology" due to small inclusions in the Dungeon Master's Guide (2008) and Manual of the Planes.

[16] Trenton Webb of British RPG magazine Arcane calls the city "splendidly bizarre" and declares that "Sigil, The Lady of Pain's citadel, is an elegant gaming construct, yet it can often feel a little hollow", feeling that life in Sigil should be "a swirl of plots, factions and sedition that leaves players' heads spinning, wounds bleeding and experience points tally in overdrive".

[17] Sigil as depicted in Planescape: Torment was praised by Evan Narcisse from Kotaku as one of the richest science fiction and fantasy worlds in video games.

It could also provide a resting point between adventures, allowing the party to catch their breath between forays into D&D's dangerous outer planes".

[20] Chroniclers of D&D's art Michael Witwer et al. counted the depictions of Sigil among Planescape's "haunting visual dreamscapes" and stated that the city as well as the character of the Lady of Pain "were burned permanently into the lexicon of Dungeons & Dragons.