Abstract: This article critically examines two doctrines that States have used to declare exceptional maritime sovereignty: Historic Waters and Ancient Title. Despite their long pedigree in customary international law, I argue that both doctrines are largely irrelevant in the modern regime of maritime delimitation established by the United Nations Convention on the Law of the Sea (UNCLOS). Analysis of the negotiating record shows that UNCLOS was negotiated as a package deal, creating a novel and holistic regime for maritime delimitation that was responsive to the international community's pressing concern with overfishing, pollution, freedom of navigation, and greater equality of economic rights. Both historic waters and ancient title would derogate from this negotiated regime as they are incompatible with the objective criteria UNCLOS uses to demarcate maritime sovereignty and jurisdiction. Furthermore, I argue that historic water and ancient title can only be applied in the context of historic bays as this is explicitly allowed in UNCLOS article 10. Additionally, provisions in which UNCLOS allows consideration of 'historic title' should not be understood to incorporate the doctrines of historic waters and ancient title into modern maritime delimitation. Instead, they should be interpreted as allowing States and tribunals room for limited equitable consideration of historic practice when contemplating minor adjustments to maritime boundaries established by UNCLOS' objective principles. These conclusions are far from a theoretical curiosity. For example, the limited degree to which international law countenances exceptional maritime claims based on historic waters and ancient title will have profound implications for States claiming broad historic entitlement in the South China Sea.