Karol Adwentowicz (19 October 1871 – 19 July 1958) was a Polish actor and theater director. Adwentowicz fought in the Polish Legions in World War I, and upon the return of Poland's sovereignty, embarked on a hugely successful touring career across the country. During the Nazi occupation of Poland he was imprisoned in Pawiak, part of the Warsaw concentration camp. He died in Warsaw, two years after the Polish October.

Adwentowicz directed plays and performed in several theaters both before and during the war, including at the Słowacki Theatre in Kraków in 1912 commissioned by Ludwik Solski. In the interwar Poland he run the experimental Ateneum Theatre in Warsaw along with Stefan Jaracz (1933–34 season), but also founded the Teatr Kameralny in the city. Adwentowicz was one of the most recognized dramatic actors in contemporary Poland, particularly for his role as Hamlet.