Sijjin (Arabic: سِجِّين‎ lit. Netherworld, Underworld, Chthonian World) is in Islamic belief either a prison, vehement torment or straitened circumstances at the bottom of Jahannam, i.e. Gehenna or hell, below the earth (compare Greek Tartarus),[1][2] or, according to a different interpretation, a register for the damned or record of the wicked,[3] which is mentioned in Surah al-Muṭaffifīn (83:7–9) of the Quran. The antithesis of Sijjin is Illiyin.