Portugal: Grândola, Vila Morena - Zeca Afonso. Probably not a hit when it came out, as it was banned by the dictatorial regime at the time but it became the anthem of our 1974 revolution, pretty much because it was the song that the revolutionary group chose to be played on the radio station (they took control of) to mobilize their forces.
Zeca Afonso has a bunch of other well-known (and really good) songs, all sung in Portuguese but this is the one most people know by heart. It helps that it gets played every year on the anniversary of the revolution and whenever there's a protest.