Karol Marcinkowski (23 June 1800 in Posen, Kingdom of Prussia, today Poznan in Poland–6 November 1846) was a Polish physician, social activist in the Greater Poland region (also called the Grand Duchy of Posen), supporter of the basic education (Praca organiczna) programmes, organizer of the Scientific Help Society (Towarzystwo Pomocy Naukowej) and the Poznan Bazar (Bazar Poznanski) - the Polish mall in Poznan that included a hotel, meeting rooms, crafts and shops.