The Fifth Regiment (Spanish: Quinto Regimiento, the full name Quinto Regimiento de Milicias Populares, was an elite corps loyal to the Spanish Republic at the onset of the Spanish Civil War. Made up of volunteers, the Fifth Regiment was active in the first critical phase of the war and became one of the most renowned units loyal to the Republic. The Fifth Regiment used the desecrated building of the Church of San Francisco de Sales in Madrid as its headquarters. The mouthpiece of this military unit was the newspaper and its anthem the El quinto regimiento song.