Mechanochemistry has emerged as a powerful and sustainable technology in modern synthetic chemistry, offering not only a drastic reduction in solvent usage but also accelerated reaction rates and enhanced robustness. The remarkable stability of solvent-free ball-milling reactions becomes particularly evident in transition-metal catalysis. Whereas many palladium-catalyzed cross-coupling reactions in solution require rigorous exclusion of air and moisture to avoid catalyst degradation, numerous analogous transformations can be performed mechanochemically under ambient conditions without loss of activity. Over the past years, various mechanochemical protocols for palladium-catalyzed cross-couplings have been developed using powdered (pre)catalysts, with or without additional ligands. However, as in solution-phase catalysis, the active complex often deactivates after the reaction, rendering catalyst recovery and reuse challenging. To address this limitation and to combine facile catalyst recycling with the robustness and efficiency of mechanochemical transformations, we have pioneered the concept of direct mechanocatalysis. In this approach, the metallic milling media – either the ball or the vessel itself – acts simultaneously as the catalyst and the mechanical driver of the reaction. Using this concept, we established solvent-free, direct mechanocatalytic protocols for key transition-metal-catalyzed C–C bond-forming reactions, including the Suzuki, Sonogashira, and Mizoroki–Heck couplings. These reactions proceed efficiently using a single palladium milling ball in a polymeric milling jar, which serves both as the catalytic site and the energy transfer medium. Surface analyses of the catalytically active milling ball revealed mechanistic parallels to solution-based catalysis, confirming that well-known pathways are operative on the metallic surface. Importantly, the palladium milling ball can be removed easily from the reaction mixture and reused in subsequent reactions without regeneration. Beyond C–C coupling chemistry, we also demonstrated that not only the milling ball but also the inner surface of metallic milling vessels can serve as an active catalytic interface. For instance, selective oxidation of primary alcohols to aldehydes proceeds efficiently on the gold surface of the milling jar.[6] These results highlight the broad potential of direct mechanocatalysis as a sustainable and versatile platform for heterogeneous transition-metal catalysis in the solid state.