High turnout was expected in a vote pitting leaders of the wealthy northeastern region's separatist movement against parties that want to remain in Spain.
Catalonia's sacked leader on Tuesday called on pro-independence parties to unite for next month's regional election as he aims to recapture power and push on with a divisive secession bid.
No one knows how the crisis will end, but many Catalans feel it has been a long time coming.
An address by separatist leader Carles Puigdemont, initially scheduled for 1:30 pm on Thursday, has since been suspended without explanation.
A far-left Catalan party today threatened "massive civil disobedience" if Spain dismisses the region's government to stave off its threat to declare independence.
Two key allies of Catalan president Carles Puigdemont called on him not to waste any more time, and to ignore the Spanish government's threats
Catalan leader Carles Puigdemont said Saturday he and his supporters would not "give up" their rights, speaking on the eve of an independence vote.
Seven and a half million people in Catalonia will take part in a referendum condemned as illegal by Spain's Constitutional Court.
Catalan separatists were determined to press ahead with an independence referendum banned by Madrid.
The electoral board set up to oversee the vote has been dissolved, and on Tuesday prosecutors ordered police to seal off places to be used as polling stations and guard them until Sunday.