In November 2014, Catalonias' government held an informal referendum in which more than 80% voted in favor of independence.
It has since fought for the right to hold a legally binding vote and is pushing ahead with a referendum on Sunday despite the firm opposition of the Spanish government.
The Spanish leadership has rejected the vote as illegal and the courts have ordered a halt. Spanish police have arrested senior Catalan officials, seized ballots and raided key regional buildings in an attempt to stop it going ahead.
Catalans have taken to the streets in protest. So what has stirred this hunger for independence - and could it happen?

WHERE IS CATALONIA?

Catalonia is one of Spain's wealthiest and most productive regions and has a distinct history dating back almost 1,000 years.
At the northeastern region of Spain is home to 7.5 million citizens and has its own devolved government.
It has its own language, cultural traditions and the country's second biggest city, Barcelona.
Antecedent to the Spanish Civil War (1936-39) the region was given broad right for external government, but this was rolled back under the dictatorship of Francisco Franco.
Catalonia regained autonomy after General Franco's death in 1975, then secured enhanced judiciary and taxation powers following a landmark vote in 2006.
However, in July 2010 Spain's constitutional court ruled that parts of the region's autonomy statute were unlawful and that references to Catalonia as a nation had "no legal validity".

WHAT IS THE QUESTION?
The Catalan parliament enacted its own law in a vote on 6 September. There is just one question on the ballot paper:
"Do you want Catalonia to become an independent state in the form of a republic?"
And there are two boxes: Yes or No.
Under the controversial law, the result is binding and independence must be declared by parliament within two days of the Catalan electoral commission proclaiming the results.

WHAT DOES THE GOVERNMENT HAS TO SAY?

Since the nation's constitutional court declared the referendum illegal, Madrid has launched a crackdown to confiscate millions of ballot slips.
State police have been sent to the region to monitor public spaces and "act in case the illegal referendum is maintained", sparking protests in Barcelona and other cities.
Madrid has moved to put Catalan forces in the area under central control.
Spanish Prime Minister Mariano Rajoy has said he will "do whatever is needed, without renouncing anything" to prevent the referendum going forward.
Foreign minister Alfonso Dastis claimed separatists were using "Nazi" tactics to intimidate opponents, adding: "Referendums are a weapon of choice of dictators".

WILL THERE BE VOTING?
Voting will certainly take place in some form in some areas, but the national authorities have brought in 4,000 police from outside Catalonia to help thousands of local Mossos police and national officers to keep security and stop the vote.

WHAT WILL HAPPEN IF CATALONIA VOTES FOE INDEPENDENCE?

While former prime minister David Cameron promised the Scottish referendum was "decisive and irreversible", Catalonia's vote is anything but clear cut.
Separatists are holding the ballot against the wishes of the Spanish government, which is certain to block a move for independence in the event of a 'yes' vote.
However, the Catalan government says the vote is legally binding and if separatists are successful independence must be declared by parliament within two days of the result.
The referendum has a large amount of symbolic significance.
A 'yes' vote would add fuel to the fire but even without it independence campaigners have taken advantage of the police crackdown, which they claim has suppressed democracy.
Protesters have called for an "unstoppable wave of democracy", while Catalan President Carles Puigdemont warned the Spanish government: "You can't stem the tide".