Bandera Negra (Black Flag) or Santa Germandat Catalana (Holy Catalan Brotherhood) was the secret, armed sub-organization of the Estat Català political party, founded on May 3, 1925.

Its name referred to the black flag raised by the defenders of Barcelona in the Catalan Campaign (1713-1714) on August 1, 1714, signaling to the Bourbon troops that they would fight to the death and never surrender.

[2] Historian Enric Ucelay-Da Cal explains how Bandera Negra was born:[2] In Bertrellans Street, a dark alley parallel to the commercial street (then in full development and construction) of Portal de l'Àngel, there was a flat with a small excursion group called the Serra del Cadí.

With that intention, they took on a clandestine identity and defined themselves as a "secret Catalan brotherhood" with the sonorous and threatening name of Black Flag...

The most notable head of the organization was Marcel·lí Perelló, together with Jaume Compte (also a member of the Autonomous Center of Trade and Industry Dependents).