Petr Placák (born 8 January 1964 in Prague), also known under pseudonym Petr Zmrzlík, is a Czech writer.
During the communist regime in Czechoslovakia he published his works in samizdat.
He was clarinettist in the Plastic People of the Universe since 1983 and recorded two albums with this band: Hovezí porážka (1982) and Pulnocní myš (1986).
Later he worked as a journalist for many newspapers, such as Respekt and Lidové noviny.