Abstract How do actors weaponize water in intrastate conflicts? Existing typologies of water weaponization make deterministic differentiations between state and non-state actors and invoke opaque labels like ‘terrorism’. Furthermore, these typologies ignore how various actors engaged in violent conflict also cooperate over water, and whether water weaponization occurs beyond war. I propose a new typology for water weaponization in an analysis of the case of Syria, drawing on the leaked ‘ISIS papers’ as well as primary sources and interviews. The study begins by charting how the Ba'athist regime used water as a weapon of domination and legitimacy against its Kurdish population with infrastructure that would later facilitate the Islamic State of Iraq and Syria's (ISIS) ability to take hold of northeast Syria. I then turn to how non-state armed groups like ISIS and the Kurdish Democratic Union Party (PYD) have adopted strategies of water weaponization similar to the Syrian government by targeting and channelling water systems with major tactical implications. Finally, I show how enemy parties such as ISIS and the al-Assad regime weaponized cooperative water agreements to advance their mutual interests with violent implications for civilians. As such, I sort strategies of water weaponization into four categories: domination and legitimacy, military tools, military targets, and cooperation. In doing so, this new typology makes three main contributions, by: 1) accounting for how water is weaponized in state-society relations outside conflict; 2) refining existing definitions of water as a military tool and target; and 3) appraising the weapon-like effects of water cooperation.