The Penó de Santa Eulàlia, St Eulalia's Banner, is the historical flag of Barcelona, and one of its main symbols. The city's patron saint is represented by a figure or a saltire, the saint's main symbol, on a claret background. These days, the flag flies over the City Hall balcony every 12 February, the feast day of Santa Eulalia. The act of raising the banner is one of the oldest and most solemn of the main winter festival. In the morning of Santa Eulàlia's Day, the mayor hangs the flag to the sound of Els Segadors, the Catalan national anthem, while the policemen of the Guàrdia Urbana and the Mossos d’Esquadra stand to attention.

There are two versions of the same emblem: As a banner and as a flag. The banner is the ancient military standard, and is lighter; the flag is bigger and is used ceremonially. The Penó de Santa Eulàlia is historically very significant because it was flying from the balcony of City Hall in July 1713 when, in the middle of the War of Succession, the Council of One Hundred decided to resist. It was also the standard brandished by Rafael de Casanova when he was injured during the attack in the final defence of the city on 11 September, 1714.