Yukio Hatoyama is the grandson of a former prime minister
Japan's opposition Democratic Party has chosen Yukio Hatoyama, the grandson of a former prime minister, as leader ahead of elections later this year.
Mr Hatoyama succeeds Ichiro Ozawa, who stepped down amid a fundraising scandal on 11 May.
The new opposition leader has pledged to cut wasteful spending.
Opinion polls suggest the Democrats are ahead of PM Taro Aso's Liberal Democratic Party, which has ruled for some 50 years, with one short break.
Mr Hatoyama, 62, won a swiftly organised election among Democratic Party members of Japan's Diet, or parliament.
Mr Ozawa had been under pressure to resign after a close aide was charged in a fundraising scandal in March.
Tokyo prosecutors alleged Mr Ozawa's political funding organisation received 21 million yen ($216,000; £142,000) in illegal donations from Nishimatsu Construction between 2003-07.
Before the scandal broke, Mr Ozawa had been thought likely to unseat the beleaguered prime minister, Taro Aso, in parliamentary elections.
But opinion polls have suggested his popularity had waned as a result of the scandal.
Mr Hatoyama's party has promised to loosen the bureaucracy's grip on policy making and pursue more assertive diplomacy towards Japan's security ally the United States.
But the BBC's Roland Buerk in Tokyo says Mr Hatoyama may struggle to bring change to Japanese politics, which is dominated by wealthy political dynasties.