Oskar Paul Dirlewanger (26 September 1895 – c. 7 June 1945) was a German military officer, convicted child molester, and war criminal. He is best known for commanding the Dirlewanger Brigade, a penal military unit of the Waffen-SS which served in World War II. His unit committed some of the conflict's most infamous atrocities, with Dirlewanger himself regarded as perhaps Nazi Germany's "most extreme executioner", engaging in constant acts of violence, rape, and murder. He died after the war while in Allied custody.

Dirlewanger had an impressive career as a junior officer during World War I. He further fought in the post-World War I conflicts in Germany as a minor commander in the Freikorps militia movement, with the troops he led then also characterized by excessive violence, and participated in the Spanish Civil War. He was also a habitual offender, convicted in interwar Germany for raping a child and other crimes. During World War II, Dirlewanger was appointed and headed a special Waffen-SS unit that was officially named after him and was composed for the most part of conscripted convicts and other prisoners.

Serving mostly in Poland and Belarus, Dirlewanger has been closely linked to many atrocities, being responsible for the deaths of at least tens of thousands. His methods included rape and torture, and he personally kept numerous women as his sex slaves. He is also noted to have committed the worst crimes of the bloody suppression of the Warsaw Uprising. Dirlewanger's brutality was not limited to civilians and captured enemy combatants, as he was ruthless to his men, whom he would beat and kill if they displeased him. His unit is regarded as the war's most infamous in Belarus, as well as Poland, and arguably the worst military force in modern European history based in terms of criminality and cruelty.