Entanglement and Nonlocal Coherence: Why Nonlocality Is Natural in a Phase Ontology (Phase Ontology — Part IV) reframes quantum entanglement by changing the usual starting assumption. The paper argues that entanglement only looks paradoxical if spacetime separation is assumed to imply ontological separation. If phase coherence is treated as a primary layer of reality (as developed in Parts I–III), then nonlocal correlations become expected rather than mysterious. In this view, entangled systems share a single coherent phase structure prior to measurement. Measurement is described as local phase locking: an interaction with a detector stabilizes a definite outcome locally, while the joint correlations arise because both outcomes are constrained by the same underlying phase structure. No superluminal signal is required; correlations are revealed rather than transmitted. The paper also addresses compatibility with relativity: since no information is communicated faster than light, relativistic causality remains intact. Locality is treated as an emergent property of spacetime, while coherence relations can be nonlocal because they are not fundamentally “in spacetime” to begin with. This manuscript is Part IV of a seven-part series (Parts I–VII). It connects the measurement framework of Part III to entanglement and points ahead to Part V (time, irreversibility) and Part VII (experimental implications and falsifiability).