This article explores the relationship between international humanitarian law (IHL) and the State sovereignty. Historically, only wars between sovereign States were subject to regulation by the laws of war. From the 19th century onwards, States agreed upon a significant number of IHL treaties and in 1949, despite calls upon sovereignty, they accepted extension of a limited part of the rules to non-international armedconflicts. Since then, through the formation of customary international law and in part as result of new treaties, it has been accepted that the majority IHL has become applicable to internal conflicts. In addition, international institutions have been set up to prosecute individuals for serious violations of IHL. The author discusses how IHL and sovereignty have influenced each other’s development. The analysis shows that the development of IHL should not be seen as limiting State sovereignty, but rather ought to be regarded as a manifestation of sovereignty, expressed through the formation of this branch of international law by its core subjects: States. At the same time, as a result of the increased reliance on means other than treaties for clarification and development of IHL, the role of States has become more limited; it is reduced to either accepting or rejecting the prospective developments of IHL and any consequential impact on their sovereignty.