Stefan Konstanty Myszkiewicz-Niesiolowski (Polish pronunciation: ['st?fan ?e??'w?fsk?i], born 4 February 1944) is a Polish politician and member of the Union of European Democrats.
In 1970, Niesiolowski 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, Niesiolowski joined the Independent Self-governing Trade Union "Solidarity".
During the martial law, Niesiolowski was imprisoned in Jaworze for around a year.