World War II saw the largest scale of war crimes and crimes against humanity ever committed in an armed conflict, mostly against civilians and specific groups (e.g. Jews, homosexuals, people who are mentally ill or disabled) and POWs. The war also saw the indiscriminate mass rape of captured women, carpet bombing of civilian targets and use of starvation as weapon of war.

Most of these crimes were carried out by the Axis powers who constantly violated the rules of war and the Geneva Convention on Prisoners of War, mostly by Nazi Germany and the Empire of Japan. Dutch historian Pieter Lagrou observed that "forced labor carried out in murderous circumstances by Allied soldiers and civilians in Japanese hands", alongside the murder of millions of Soviet POWs by the Germans, "are among the most infamous crimes of the Second World War".^: 4

However the decision by the United States to drop nuclear bombs on Hiroshima and Nagasaki is still debated to this day on whether it could amount to war crimes or crimes against humanity.

This is a list of war crimes committed during World War II.