Release Dates
| Canada | 8 September 2003 | (Toronto International Film Festival) |
| Canada | 19 September 2003 | |
| UK | 19 September 2003 | |
| Ireland | 19 September 2003 | |
| USA | 19 September 2003 | |
| France | 24 September 2003 | |
| Lithuania | 29 September 2003 | (Forum Cinemas Cinema) |
| Philippines | 1 October 2003 | (Manila) |
| Greece | 3 October 2003 | |
| Iceland | 3 October 2003 | |
| Lithuania | 3 October 2003 | |
| Israel | 9 October 2003 | |
| South Korea | 10 October 2003 | |
| Belgium | 15 October 2003 | |
| Russia | 16 October 2003 | |
| Spain | 17 October 2003 | |
| Switzerland | 22 October 2003 | (French speaking region) |
| Finland | 25 October 2003 | (Night Visions Film Festival) |
| Philippines | 30 October 2003 | (Davao) |
| Finland | 21 November 2003 | |
| Bahrain | 26 November 2003 | |
| Czech Republic | 27 November 2003 | |
| Poland | 28 November 2003 | |
| Japan | 29 November 2003 | |
| New Zealand | 4 December 2003 | |
| Denmark | 5 December 2003 | |
| Norway | 5 December 2003 | |
| Kazakhstan | 12 December 2003 | |
| Colombia | 19 December 2003 | |
| Egypt | 7 January 2004 | |
| Netherlands | 15 January 2004 | |
| Portugal | 15 January 2004 | |
| Australia | 22 January 2004 | |
| Switzerland | 29 January 2004 | (German speaking region) |
| Germany | 29 January 2004 | |
| Austria | 30 January 2004 | |
| Italy | 30 January 2004 | |
| Turkey | 30 January 2004 | |
| Kuwait | 24 February 2004 | |
| South Africa | 5 March 2004 | |
| Sweden | 19 March 2004 | |
| Slovakia | 26 March 2004 | |
| Mexico | 7 April 2004 | |
| Brazil | 16 April 2004 | |
| Hungary | 22 April 2004 | |
| Argentina | 20 May 2004 | |
| Panama | 11 June 2004 | |
| Bulgaria | 16 July 2004 |
Also Known As (AKA)
| Argentina | Inframundo |
| Bulgaria (Bulgarian title) | Подземен свят |
| Brazil | Anjos da Noite |
| Canada (French title) | Monde infernal |
| Germany | Underworld |
| Spain | Underworld |
| Finland | Varjojen valtakunta |
| France | Underworld |
| Greece | Underworld |
| Croatia | Underworld |
| Hungary | Underworld |
| Lithuania | Kitas pasaulis |
| Panama | Inframundo |
| Portugal | Underworld - O Submundo |
| Serbia | Podzemni svet |
| Russia | Другой мир |
| Slovenia | Podzemlje |
| Turkey (Turkish title) | Karanliklar ülkesi |