Tadeusz can refer to:
- Tadeusz Bór-Komorowski, Polish military leader
- Tadeusz Borowski, Polish writer and Holocaust survivor.
- Tadeusz Boy-Żeleński, Polish gynaecologist, writer, poet, art critic, translator of French literary classics and journalist
- Tadeusz Brzeziński, Polish consular official and the father of President Jimmy Carter's national security adviser, Zbigniew Brzezinski
- Tadeusz Czeżowski, Polish philosopher and logician
- Tadeusz Dołęga-Mostowicz, Polish journalist and author of over a dozen popular novel]s
- Tadeusz Drzazga, Polish weightlifter
- Tadeusz Kassern, Polish composer
- Tadeusz Wladyslaw Konopka, American actor
- Tadeusz Konwicki, Polish writer
- Tadeusz Kościuszko, Polish national hero
- Tadeusz Kotarbiński, pupil of Kazimierz Twardowski
- Tadeusz Krwawicz, Polish pioneer in medicine
- Tadeusz Kurcyusz, commandant of Narodowe Sily Zbrojne
- Tadeusz Łomnicki, Polish actor
- Tadeusz Miciński, Polish poet and playwrigh
- Tadeusz Rejtan, Polish nobleman
- Tadeusz Różewicz, Polish poet and writer
- Tadeusz Rut, Polish hammer thrower
- Tadeusz Sapierzyński, Polish army officer
- Tadeusz Swietochowski, American historian and Caucasologist
- Tadeusz Ślusarski, Polish Olympic gold medalist in pole vault at the 1976 Olympics
- Tadeusz Tański, Polish automobile engineer and the designer of, among others, the first Polish serially-built automobile
- Tadeusz Tomaszewski, Polish politician, Member of the Parliament
- Tadeusz Ważewski, Polish mathematician
- Tadeusz Żychiewicz (1922–1994), Polish journalist, art historian and publicist
In culture Tadeusz can refer to:
- Pan Tadeusz, an epic poem by Adam Mickiewicz