Prime Minister Julia Gillard says the federal election will be held on Saturday, September 14.
Ms Gillard made the surprise announcement during an address to the National Press Club in Canberra on Wednesday.
The Labor leader said she wanted to avoid the "carry on" that usually arises from constant speculation of the likely date of the poll during an election year.
She said wanted to create an environment in which voters could be more easily focused on national issues, rather than "petty politics".
"I can act so Australia's parliament and government serves their full three-year term, so it is clear and certain when the election will be held," Ms Gillard said.
"So today I announce that I will advise the governor-general to dissolve the House of Representatives and issue the writs on Monday, August 12 for an election for the house and half the Senate to be held on Saturday, the 14th of September."
"I do so not to start the nation's longest election campaign, quite the opposite," Ms Gillard said.
"It should be clear to all which are the days of governing, and which are the days of campaigning."
Announcing the election date now would also enable individuals, businesses and investors to plan out their year with some certainty.
"It gives shape and order to the year, and enables it to be one not of fevered campaigning, but of cool and reasoned deliberation," she said.
Ms Gillard said Australians weren't interested in campaigns without content, or platitudes devoid of purpose.
"There is now clearly the time and certainty necessary for the people and parties contesting the election to lay out their fully detailed, costed plans for the timely consideration of voters," she added.
Federal NSW Independent MP Tony Windsor welcomed the announcement of the election day, saying calling it now would provide certainty.
"In the past, Australians have been frustratingly on 'election alert' for long periods of time and, in this 'hung' parliament, on the brink of an election from day one if you believe the Opposition Leader and some sections of the media," he said in a statement.
But Mr Windsor admitted the early announcement would mean the next eight months might well see both major parties in campaign mode.
Fellow Independent MP Rob Oakeshott said the poll date was in line with the agreement reached with crossbench MPs after the 2010 election.
"This parliament will run its full term and the election will be held as agreed," he said in a statement.
Parliament resumes next week and there are about nine sitting weeks before September 14.
Opposition Leader Tony Abbott was on a plane out of Melbourne when Ms Gillard named the election date.
Ms Gillard said by announcing the date so far in advance, the opposition no longer had an excuse not to provide detailed costings ahead of the poll.
"They have two things that an opposition has never had before to enable them to do that," she said.
"One, they've got the benefit of a fixed election date now with several months notice.
"Two, because of what we've done with the Parliamentary Budget Office they've got more resources available to them than an opposition has ever had before in the history of the nation to produce proper costings."
Liberal frontbencher Steve Ciobo used Twitter to respond to the announcement.
"So, the Fed Election is on Sept 14 - how much more damage can Labor do in 7 months?" he tweeted.
Ms Gillard said there were only a limited number of dates.
"I reflected on this over the summer and I thought it's not right for Australians to be forced into a guessing game and it's not right for Australians to not face this year with certainty and stability," she said.
She said she had consulted with her deputy Wayne Swan and her senior colleagues about the date.