The laws of war are a body of laws on acceptable justifications for going to war (jus ad bellum) and about the limits of acceptable conduct during a war (jus in bello). The laws of war are part of public international law.

Among other issues, the modern laws of war refers to declarations of war, acceptance of surrender and the treatment of prisoners of war, military necessity, including aspects of distinction and proportionality, and the prohibition of weapons which may cause unnecessary suffering.