A Theory of Dark Matter proposes a comprehensive framework to explain recent high-energy astrophysical observations, particularly the excess of positrons and electrons detected by PAMELA and ATIC. These observations suggest a WIMP with a mass of ~500-800 GeV that annihilates into leptons, with a cross section much higher than expected from a thermal relic. Signals from WMAP and EGRET support this interpretation. The presence of a new force in the dark sector, with a Compton wavelength ~1 GeV⁻¹, is inferred, allowing a Sommerfeld enhancement to boost the annihilation cross section without affecting the weak-scale cross section during freeze-out. If the dark matter annihilates into the new force carrier φ, its low mass makes hadronic modes kinematically inaccessible, favoring leptonic decay. If φ is a non-Abelian gauge boson, dark matter forms a multiplet with natural splittings of ~MeV, explaining the eXciting dark matter (XDM) scenario for the INTEGRAL 511 keV line and the inelastic dark matter (iDM) scenario for the DAMA annual modulation signal. The Sommerfeld enhancement is most significant at low velocities, potentially affecting the ionization history of the universe. The low velocity dispersion of dwarf galaxies and Milky Way subhalos can increase the substructure annihilation signal by an order of magnitude. The new force carrier φ, with a mass ~GeV, can naturally explain the observed signals, including the INTEGRAL and DAMA data. The Sommerfeld enhancement is crucial for explaining the high-energy anomalies, and the inclusion of a new force in the dark sector addresses the challenges of a large cross section into leptons and a low cross section into hadrons. The model also predicts observable effects on the cosmic microwave background and gamma-ray background, and suggests that dark matter annihilation could be detectable through various means, including gamma-ray and neutrino signals. The model is consistent with the observed data and provides a unified explanation for multiple anomalies, including the excess positrons, the WMAP haze, and the DAMA signal. The presence of a new force in the dark sector is essential for explaining these observations and provides a natural framework for dark matter interactions.A Theory of Dark Matter proposes a comprehensive framework to explain recent high-energy astrophysical observations, particularly the excess of positrons and electrons detected by PAMELA and ATIC. These observations suggest a WIMP with a mass of ~500-800 GeV that annihilates into leptons, with a cross section much higher than expected from a thermal relic. Signals from WMAP and EGRET support this interpretation. The presence of a new force in the dark sector, with a Compton wavelength ~1 GeV⁻¹, is inferred, allowing a Sommerfeld enhancement to boost the annihilation cross section without affecting the weak-scale cross section during freeze-out. If the dark matter annihilates into the new force carrier φ, its low mass makes hadronic modes kinematically inaccessible, favoring leptonic decay. If φ is a non-Abelian gauge boson, dark matter forms a multiplet with natural splittings of ~MeV, explaining the eXciting dark matter (XDM) scenario for the INTEGRAL 511 keV line and the inelastic dark matter (iDM) scenario for the DAMA annual modulation signal. The Sommerfeld enhancement is most significant at low velocities, potentially affecting the ionization history of the universe. The low velocity dispersion of dwarf galaxies and Milky Way subhalos can increase the substructure annihilation signal by an order of magnitude. The new force carrier φ, with a mass ~GeV, can naturally explain the observed signals, including the INTEGRAL and DAMA data. The Sommerfeld enhancement is crucial for explaining the high-energy anomalies, and the inclusion of a new force in the dark sector addresses the challenges of a large cross section into leptons and a low cross section into hadrons. The model also predicts observable effects on the cosmic microwave background and gamma-ray background, and suggests that dark matter annihilation could be detectable through various means, including gamma-ray and neutrino signals. The model is consistent with the observed data and provides a unified explanation for multiple anomalies, including the excess positrons, the WMAP haze, and the DAMA signal. The presence of a new force in the dark sector is essential for explaining these observations and provides a natural framework for dark matter interactions.