The topic of classification of armed conflicts between non-state groups and occupying states in cases of belligerent occupation has not received enough scholarly attention despite its possible practical importance and the fact that this issue still requires further normative clarification. This paper seeks to fill this gap. The paper focuses on the different possible ways that such armed conflicts can be classified. Among other things, the paper analyses Article 1(4) of Additional Protocol I (API) and examines its customary status. The paper also analyses how to determine which armed groups should be regarded as acting on behalf of the occupied people and suggests a novel way to interpret the ‘belonging’ requirement of Article 4A(2) of the Third Geneva Convention. Finally, the paper provides an in-depth analysis of the argument that non-state armed groups, in the context of belligerent occupation, should be considered parties to an international armed conflict even when the occupying state is not a party to API and/or refuses to acknowledge the non-state group as a party to an international armed conflict.