Catalan President Carles Puigdemont and other regional leaders have signed a declaration of independence from Spain, following the disputed referendum.
However, they say the move will not be implemented for several weeks to allow talks with the government in Madrid.
The document calls for Catalonia to be recognized as an “Independent and sovereign state”.
The move was immediately dismissed by the Spanish central government in Madrid.
A 1 October referendum in the north-eastern province which Catalan leaders say resulted in a yes vote for independence was declared invalid by Spain’s constitutional court.
Earlier, Puigdemont told the Catalan Parliament in Barcelona that the region had won the right to be independent as a result of the vote.
The referendum resulted in almost 90% of voters backing Independence, Catalan officials say. But anti-independence voters largely boycotted the ballot which had a reported turnout of 43% – and there were several reports of irregularities.
National police were involved in violent scenes as they manhandled voters while implementing the legal ruling banning the referendum.