Politics of Japan

The Constitution was promulgated on 3 November 1946 and came into force on 3 May 1947; both dates are national holidays (Culture Day and Constitution Memorial Day). It rests on three principles usually taught in Japanese schools: popular sovereignty, respect for fundamental human rights and pacifism.

Article 9 renounces war and the threat or use of force as means of settling international disputes. Successive governments have interpreted it as allowing the Self-Defence Forces, founded in 1954, and since 2015 limited collective self-defence. Amendment requires a two-thirds majority in both houses of the Diet followed by a national referendum; the text has never been amended, although revision remains a recurring political debate.

Article 1 defines the Emperor as 'the symbol of the State and of the unity of the people, deriving his position from the will of the people with whom resides sovereign power'. The Emperor has no powers related to government. He performs acts in matters of state on the advice and approval of the cabinet, such as appointing the Prime Minister designated by the Diet and the Chief Justice designated by the cabinet, promulgating laws, convoking the Diet and dissolving the House of Representatives.

Succession is governed by the Imperial House Law, which limits the throne to male descendants in the male line. Emperor Akihito abdicated in 2019 under a special law, the first abdication in about two centuries, and Emperor Naruhito acceded on 1 May 2019, beginning the Reiwa era.

The Diet (Kokkai) is defined as the highest organ of state power and the sole law-making organ of the State. It has two houses. The House of Representatives has 465 members elected for four years, most in single-member constituencies and the rest by proportional representation in eleven regional blocks; it can be dissolved early, and most general elections follow a dissolution. The House of Councillors has 248 members elected for six years, with half the seats contested every three years; it cannot be dissolved.

The lower house prevails over the upper house on the budget, treaties and the choice of Prime Minister, and can override the upper house on ordinary bills with a two-thirds majority. The Diet building in Nagatachō, Tokyo, completed in 1936, has become the shorthand for national politics itself.

Executive power is vested in the cabinet, led by the Prime Minister. The Prime Minister is designated by the Diet from among its members and formally appointed by the Emperor; in practice, the leader of the largest party or coalition in the House of Representatives becomes Prime Minister. The Prime Minister appoints and dismisses the ministers, a majority of whom must be Diet members, and all must be civilians.

The cabinet is collectively responsible to the Diet. If the House of Representatives passes a motion of no confidence, the cabinet must resign unless the house is dissolved within ten days. The ministries in Kasumigaseki, Tokyo's government district, have traditionally held great influence through their career bureaucracies.

The Liberal Democratic Party (LDP), formed in 1955 from a merger of conservative parties, has governed for most of the period since, often in coalition. The so-called 1955 system of LDP dominance was interrupted in 1993–1994 and again from 2009 to 2012, when the Democratic Party of Japan held power. Other parties span the centre-left, centre-right and left, as well as newer populist and reform parties; party names and alliances change frequently.

The electoral reforms of 1994 introduced the mixed system of single-member districts and proportional representation for the lower house. The voting age was lowered from 20 to 18 in 2016. Turnout in national elections has generally been lower than in the post-war decades.

The judiciary is independent. The Supreme Court in Tokyo, with a Chief Justice and fourteen Justices, heads a system of high courts, district courts, family courts and summary courts. The courts have the power of judicial review, though the Supreme Court has used it sparingly. Supreme Court Justices face a retention vote by the people at the first general election after their appointment and every ten years thereafter.

Since 2009 citizens have served as lay judges (saiban-in) alongside professional judges in serious criminal trials. Japan retains the death penalty.

Japan has two tiers of local government. The 47 prefectures consist of one metropolis (to: Tokyo), one circuit (dō: Hokkaido), two urban prefectures (fu: Osaka and Kyoto) and 43 prefectures (ken). Each has a directly elected governor and assembly. Below them are cities, towns and villages – about 1,700 in all after mergers in the 2000s – plus Tokyo's 23 special wards, which have their own mayors and assemblies.

Large cities can be designated by cabinet order as 'designated cities', with powers close to those of a prefecture and administrative wards of their own; there are twenty, from Sapporo to Kumamoto.

The alliance with the United States, based on the Security Treaty of 1960, is the cornerstone of Japan's security policy; US forces are stationed in Japan, with a large concentration in Okinawa. Japan is a member of the United Nations (since 1956), the G7, the OECD and the Asia-Pacific Economic Cooperation forum, and a major provider of development aid.

Relations with its neighbours China, South Korea and Russia combine close economic ties with historical and territorial disputes. Japan claims the Northern Territories, held by Russia since 1945, and Takeshima, controlled by South Korea; it administers the Senkaku Islands, which China and Taiwan claim. With the European Union, Japan has an Economic Partnership Agreement, in force since 2019, and a Strategic Partnership Agreement, applied provisionally from 2019 and fully in force since 2025.