Head of state: Emperor Akihito
Akihito succeeded his father, Hirohito, in 1989. Under the 1947 constitution, Japan's emperors have a purely ceremonial role.
Prime minister: Shinzo Abe
Shinzo Abe became Japan's prime minister for the second time in December 2012, after his Liberal Democratic Party (LDP) scored a landslide election win.
He previously served a brief term as premier in 2006-7, when he was Japan's youngest leader since World War II.
He began his first term in office with a high approval rating, but a series of scandals and gaffes damaged the government, and with support for his administration plummeting, Mr Abe stepped down, citing ill health.
The centre-left Democratic Party (DPJ) came to power in August 2009 - having also won a landslide election - but quickly lost popularity as a result of a mounting financial crisis. The DPJ government also struggled to cope with the aftermath of the March 2011 tsunami, and was in its turn beset by a series of scandals.
By the autumn of 2012, faced with a "fiscal cliff" brought on by the country's public debt mountain - the highest debt to GDP ratio in the industrialised world - and the crippling after-effects of the nuclear crisis triggered by the tsunami, the DPJ had no choice but to call an early election.
On returning to the premiership in 2012, Mr Abe acknowledged the widely held perception that the LDP's sweeping victory owed a lot to anger at DPJ failures, and was not necessarily a statement of confidence in the conservative party that had previously ruled Japan almost continuously for half a century.
Known as a right-wing hawk, Mr Abe comes from a high-profile political family. His father was a former foreign minister, while his grandfather, former Prime Minister Nobusuke Kishi, was arrested as a suspected war criminal after World War II but never charged.
Shinzo Abe won his first seat in parliament in 1993 and was appointed to the cabinet for the first time in October 2005, when he was given the important role of chief cabinet secretary.
During his first premiership, he showed himself to be an outspoken populist, pushing for a more assertive foreign policy and a greater role for Japan on the world stage.
Under his administration, a bill was passed setting out steps for holding a referendum on revising the country's pacifist constitution.
He also called for a greater sense of national pride and backed a law requiring the teaching of patriotism in schools.
He provoked anger in China and South Korea when he said there was no evidence that women were forced to become sex slaves by the Japanese army during World War II. He later apologised for these remarks.
After standing down from the premiership in September 2007, he temporarily disappeared from the political spotlight. He returned to the political stage in September 2012 with his election as LDP leader, and soon expressed strong views on the ongoing territorial rows with China and South Korea.
He followed up his party leadership win with a visit in October to the controversial Yasukuni Shrine, in a move that angered neighbouring countries.
The main challenge that he faces is the still-fragile state of the Japanese economy. Even before his government was sworn in, analysts were expressing doubt over whether the steps it has pledged to take to tackle the slump would achieve the desired result. January 2013 saw Japan post a record trade deficit of $78bn (£49bn).
His first immediate challenge was a decision by a Chinese frigate to put a radar lock on a Japanese navy ship near a group of Japanese-controlled islands over which both countries, plus Taiwan, claim sovereignty. Mr Abe called it a "dangerous act" that could lead to an "unpredictable situation".