Progg was a left-wing and anti-commercial musical movement in Sweden that began in the late 1960s and became more widespread in the 1970s. Not to be confused with the English expressions "progressive music" or "prog rock," progg is a contraction of the Swedish word for musical progressivism, progressiv musik. While there were progg bands playing progressive rock, the progg movement encompassed many different musical genres.

Nationalteatern is a Swedish progg rock group from the 1970s that featured leftist political lyrics. It was originally a traveling theater ensemble with many members, most notably Ulf Dageby, Anders Melander, Totta Näslund, Nikke Ström, Hans Mosesson and Pale Olofsson.