Scotland will hold its independence referendum on 18 September 2014, First Minister Alex Salmond has announced.
The announcement starts the countdown to a vote Mr Salmond hopes will take his nation of 5m people out of the United Kingdom.
Mr Salmond's pro-independence Scottish National Party won a majority in the Scottish parliament in May 2011 elections, giving the politician what he has called a "once-in-a-generation" chance to break ties with London.
Opinion polls have put support for independence at about 30% of the electorate in Scotland, while about 50% favour the status quo.
The SNP complains that the British parliament, where members representing Scotland are a small minority because England has a much bigger population of 53 million, does not have the particular interests of the Scottish people at heart.
"A yes vote means a future where we can be certain, 100% certain, that the people of Scotland will get the government that they vote for," Mr Salmond told the Scottish parliament in a speech announcing the date of the referendum.
"The choice becomes clearer with each passing day - the opportunity to use our vast resources and talent to build a better country, or to continue with a Westminster system that simply isn't working for Scotland."
The SNP argues that North Sea Oil revenues combined with the local farming, fishing and whisky industries would enable an independent Scotland to prosper.
But other parties in Edinburgh and the London government say both Scotland and the rest of the UK would lose out.
Critics of the SNP say oil reserves are dwindling and Scotland would lose the disproportionately generous share of taxpayer money raised across Britain that it currently receives.
Scottish secession would pose serious challenges to the remainder of the UK, such as what to do about its Trident nuclear submarine fleet which is based in Scotland.
There would also be big uncertainties for Scotland itself, such as whether it would be allowed to remain part of the European Union or whether it would have to negotiate re-entry.
The broad terms of the referendum were agreed by Mr Salmond and British Prime Minister David Cameron last October.
Voters will be asked a single question: "Should Scotland be an independent country?"