A belligerent in warfare describes one of the contracting parties in the conflict; that is, one of the powers at war in contrast to neutral countries and non-belligerents.

In the written treaties of the laws of war, no distinction is made between neutral countries or neutral powers and non-belligerents for the purpose of the application of those laws and the responsibilities of belligerents toward neutral countries and vice versa.

A power not wanting to engage in a war as a contracting power (i.e., a belligerent) but sympathizing with one of the belligerents may declare itself a non-belligerent as more appropriate than neutral; however if such a nation aids a belligerent in a way proscribed to neutral nations, they risk becoming belligerents themselves.

Notwithstanding, a distinction between neutral and non-belligerent has often been drawn by nations not directly involved in a conflict to describe their positions.