The vote prompted the Spanish government to activate a constitutional mechanism that stripped the region of its autonomy, reports Efe news agency.
The rally, organised by the Catalan Civil Society platform, snaked down Paseo de Gracia, one of Barcelona's main thoroughfares, and brought together a large crowd topped with red and yellow Spanish national and official Catalan Senyera flags as well as an abundance of European Union emblems.
"We are all Catalonia," was the uniting slogan of the demonstration, which comes at a time of sky-high tensions in the affluent northeastern region of Spain following a recent independence bid that pitted separatist officials against the central government in Madrid.
According to organisers, the event attracted 1.1 million participants.
On Friday, the Catalan Parliament voted in favour of seceding from Spain and creating an independent nation in the form of a republic just weeks after the regional government, led by the then President Carles Puigdemont, pushed ahead with a referendum branded illegal by the Spanish state.
The reaction from Spain was swift. With the backing of the Senate, the conservative government of Mariano Rajoy enacted Article 155 of the Constitution -- hitherto dormant since the nation's transition to democracy some 40 years ago -- and stripped Puigdemont and his regional cabinet of their duties, dissolved the Catalan Parliament and called for fresh local elections in December.
The topic of independence has divided Catalan politics and all of the regional branches of Spain's mainstream political parties, the conservative Popular Party, the Spanish Socialist Party (PSOE) and the centre-right Ciudadanos (Citizens), walked out of the chamber ahead of the secessionist vote.
In support of the measure was Puigdemont's regional Junts Pel Si (Together For Yes, JxS) coalition government with the backing of the left-wing secessionist CUP.
The regional heads of those three pro-unity parties were in attendance at the "We are all Catalonia" march on Sunday.
The national leader of Ciudadanos, Albert Rivera, told journalists before the rally that the people would not only fill the streets of Catalonia, but also the polling stations in the snap December elections.
Puigdemont has since vowed to ignore Madrid's direct rule on Catalonia, insisting in a press conference on Saturday that he would continue to work towards creating an independent state.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
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