Stefan Konstanty Myszkiewicz-Niesiołowski (born 4 February 1944) is a Polish politician and member of the Union of European Democrats. In 1970, Niesiołowski became involved in anti-communist opposition Ruch. He was the main proponent of burning down the Lenin Museum in Poronin, for which he was sentenced to 7 years imprisonment in 1971, and was released under amnesty in 1974. In 1980, Niesiołowski joined the Independent Self-governing Trade Union "Solidarity". During the martial law, Niesiołowski was imprisoned in Jaworze for around a year.