The standard cosmological model, ΛCDM, successfully describes cosmic acceleration, but it treats dark energy as an independent and poorly understood component of the universe. In this paper, we show that dark energy is not a fundamental entity separate from matter, but is instead the total gravitational self-energy (GSE) inherent to matter itself. Matter-Only Cosmology (MOC) expresses the dark energy density solely as a function of the matter density ρ_m and the compactness ratio R_S/Χ_p, without introducing new fundamental fields. The matter-induced dark energy density is given by ρ_{Λ_m}=(βρ_m/2)(R_S/Χ_p)[(5β/14)(R_S/Χ_p)-1], where R_S=2GM/c^2 is the Schwarzschild radius of the causally connected mass and Χ_p is the comoving particle horizon. Thus, the compactness ratio determines the transition between the attractive and repulsive GSE regimes. Because ρ_{Λ_m} is explicitly tied to ρ_m, dark energy is reinterpreted as a matter-induced form of energy rather than as an independent energy component. The dark energy density is negative in the early universe, thereby enhancing structure formation, before later transitioning to a positive phase that drives cosmic acceleration. In this way, MOC naturally addresses the Hubble tension, the existence of massive galaxies in the early universe, the observed present-day dark energy density, its late-time quasi-constant behavior, recent indications of a weakening dark energy component, and the cosmological constant coincidence problem. Moreover, MOC unifies inflation and late-time cosmic acceleration under the same GSE principle, and it provides a natural built-in termination mechanism for primordial inflation. Finally, by predicting macroscopic non-singular cores inside black holes, MOC offers a physically motivated route toward resolving the black hole information paradox. By expressing dark energy as an explicit function of the matter density ρ_m and the compactness R_S/Χ_p, the MOC framework transforms it from a phenomenological parameter into a predictive and falsifiable physical quantity.