2005 Japanese general election

General elections were held in Japan on 11 September 2005 for all 480 seats of the House of Representatives, the lower house of the Diet, almost two years before the end of the term taken from the previous elections in 2003. Prime Minister Junichiro Koizumi called the election after bills to privatize Japan Post were voted down in the upper house (which cannot be dissolved), despite strong opposition within his own Liberal Democratic Party (Japan) (LDP).

The elections resulted in a landslide victory to Koizumi's LDP, with the party winning 296 seats, the largest share in postwar politics and the first time the LDP had won an overall majority in the House of Representatives since 1990. With its partner, New Komeito, the governing coalition then commanded a two-thirds majority in the lower house, allowing them to pass legislative bills over the objections of the upper house and (though the government did not attempt this) to approve amendments to the Constitution, then submit them to the upper house and a national referendum.

The opposition Democratic Party (DPJ), which advocated a change of government during campaign, suffered a devastating loss, winning only 113 seats against 175 seats it held going into the election. The setback led the DPJ leader Katsuya Okada to resign, and raised a question whether the DPJ could remain an alternative to the LDP in the future elections.

The small parties made only small gains or losses, with Koizumi's ally, New Komeito, falling slightly from 34 seats to 31. Of the new parties contesting the election, the New Party Japan fell from three seats to one, while the People's New Party was unchanged at four seats. The Japanese Communist Party held its ground with nine seats, while the Social Democratic Party won seven, a gain of one.