This work presents the Relativistic Coherent Vacuum Gravity Theory (rCVGT), a covariant extension of the original Coherent Vacuum Gravity Theory (CVGT). The model introduces a vacuum-coherence field ψ, a vacuum-flow four-vector u^μ, and a time-rate field τ, all coupled to the metric through a unified relativistic action. These fields generate additional contributions to the stress–energy tensor, modifying gravity in both static and cosmological contexts.The theory reproduces Newtonian gravity in the weak-field limit and recovers CVGT as a non-relativistic approximation, while predicting new effects such as coherence-induced antigravity, dark-matter-like halo formation, refractive gravitational-wave propagation, and variable cosmic acceleration.The document includes full field equations, weak-field expansions, cosmological implications, observational signatures, toy models, stability analysis, and extended derivations. Appendices provide modified Friedmann equations, halo solutions, perturbation theory, and a quantum-field interpretation linking vacuum coherence to Casimir-like energy shifts and squeezed-state structures.