Japanese Prime Minister Shinzo Abe has called an election a year early and will dissolve parliament on Thursday.
Mr Abe said he was seeking a fresh mandate to overcome "a national crisis" amid rising threats from North Korea.
His decision comes amid rebounding approval ratings after a record low over the summer and with the opposition largely in disarray.
Mr Abe did not set a date for the vote but Japanese media suggest it will be on 22 October.
Mr Abe's support has surged as rising tensions with North Korea have overshadowed criticism of alleged cronyism.
The prime minister also announced a 2tn yen ($17.8bn, £13.2bn) stimulus package on education and social spending.
In a press conference on Monday evening, he said the fresh stimulus was needed for programmes to prepare Japan for the future.
He also said he would continue on his path of fiscal reform and would use the revenue from the recently introduced sales tax to balance the budget and reduce debt.
Why snap elections?
Analysts see the early vote as his way to seize the resurgent support and exploit the current weakness of the opposition.
For months, Mr Abe's popular support has been badly hit by a string of scandals and unpopular policies.
In July, his ratings had dropped to less than 30% but then recovered to above 50% in September.
He denies allegations of cronyism and on Monday said dissolving the lower house was not an attempt at avoiding those allegations.
Mr Abe is also is trying to push through a controversial shift in Japan's post-war pacifist defence policy, calling for formal recognition of the military in the constitution.
Who will he be running against?
While Mr Abe's tough stance on North Korea has helped him regain support, his Liberal Democratic Party's (LDP) campaign is also expected to focus on social policies at home.
The main opposition Democratic Party went through a tumultuous leadership resignation in July and is currently struggling with single-digit poll ratings.
But Mr Abe faces a new challenge from a former LDP cabinet member, current Tokyo Governor Yuriko Koike, who earlier on Monday announced she was forming a new national political party.
If current opinion polls are confirmed at the ballot box in October, Mr Abe will remain prime minister but his current coalition with the smaller Komeito party might fail to secure the two-thirds majority needed for his plan to revise the constitution.
If he wins another term, it would put Mr Abe on track to becoming the country's longest-serving political leader in Japan's post-war history.