Incumbents
- Emperor: Akihito
- Prime Minister: Junichiro Koizumi (L–Kanagawa)
- Chief Cabinet Secretary: Hiroyuki Hosoda (L–Shimane) until October 31, Shinzo Abe (L–Yamaguchi)
- Chief Justice of the Supreme Court: Akira Machida
- President of the House of Representatives: Yōhei Kōno (L–Kanagawa) until August 8 and again from September 21
- President of the House of Councillors: Chikage Ōgi (L–proportional)
- Diet sessions: 162nd (regular, January 21 to August 8), 163rd (special, September 26 to November 1) – 162nd and 163rd Diet are also often referred to as yūsei kokkai, "postal Diet"
Read more about this topic: 2005 In Japan