The marchers carried red, yellow and blue Catalan flags and chanted slogans calling for the northeastern autonomous community to break away from Spain.
The rally, known as the "Diada," commemorates the fall of Barcelona to Bourbon troops in 1714 during the Spanish War of Succession.
Attendance at such pro-independence demonstrations has fallen in recent years, along with support for the region's secessionist campaign.
This year's rally comes as Madrid appeals to the two main Catalan parties for help in forming government following an inconclusive election in July. Acting Prime Minister Pedro Sanchez needs the support of the secessionist parties to secure a governing majority.
What are the Catalan parties' demands?
Last week, Carles Puigdemont, the exiled former leader of Catalonia, said his center-right Together for Catalonia (JuntsxCat) party could only support Sanchez in forming government if politicians who organized an independence referendum in 2017 were given amnesty.
The 2017 vote was declared illegal by Madrid but went ahead anyway. Several Catalan political figures netted rebellion convictions for organizing the referendum, prompting Puigdemont to move to Brussels to avoid prosecution.
The leader of JuntsxCat, Laura Borras, said that Catalans are not demanding a central government be formed, but want "independence."
However, she said that her party would adopt a "new strategy," and that there was an "opportunity" to reach a "historic agreement" with Madrid.
On Sunday, the current leader of Catalonia, Pere Aragones, demanded a new independence referendum.
"An amnesty alone will not resolve the sovereignty conflict with the state. Catalonia wants a free vote on independence," Aragones, who belongs to the Catalan Republican Left (ERC), said in his "Diada" address.
"Catalonia holds the keys to the state's governability. For this reason, today we must harness this strength to make possible what had not been possible until now," he stressed.
A survey published by the Catalan Centre for Public Opinion (CEO) found that 52% opposed seceding from Spain, while 42% were in favor of the autonomous region's independence.
Catalan parties become kingmakers
Alberto Nunez Feijoo's conservative People's Party (PP) will be the first to attempt to form government, as it won the most seats in the July 23 election. However, the party is unlikely to garner enough support for Feijoo to become prime minister, as it opposes giving concessions to separatist parties.
The PP won 136 seats in the lower chamber of parliament, far short of the 176 required for a governing majority. Even with the support of the far-right Vox party, it would only reach 169 seats.
Sanchez's Socialists have 121 seats in the lower house of parliament, and could form government with the support of the left-wing Sumar party, JuntsxCat, ERC and two Basque nationalist parties.
sdi/jcg (Reuters, EFE)