We introduce a theory in which gravity emerges as a thermodynamic phenomenon governed by a scalar field that sets the local rate of quantum evolution. Building on Jacobson’s thermodynamic derivation of Einstein’s equations and Verlinde’s entropic gravity, this framework extends these ideas into a unified theory of spacetime thermodynamics. In the strong-field limit it reproduces General Relativity, while in weak-field and low-density environments it predicts modified gravitational dynamics that account for galaxy rotation curves and galaxy cluster mass discrepancies without invoking particle dark matter. On cosmological scales, the theory predicts an early epoch of emergent inflation without an inflaton field and a late-time evolving accelerating expansion driven by the gradual depletion of vacuum thermodynamic capacity, implying cyclic cosmic evolution. From first principles, the framework yields parameter-free predictions for the Hubble constant and the present matter density consistent with observations. We confront the theory with Pantheon+, Cosmic Chronometers, DESI DR2 BAO, and the CMB angular scale \( \theta_\ast \), and find that it provides a statistically preferred description of the data relative to ΛCDM, with ΔBIC = -18.5, resolving the Hubble Tension as an artifact of thermodynamic evolution. These results indicate that a thermodynamic origin of gravity and spacetime offers a coherent explanation of gravitational and cosmological phenomena.