Mild metal-catalyzed C–H activation has emerged as a promising area in organic chemistry, offering efficient and selective transformations under mild conditions. This review highlights recent advancements in this field, focusing on reactions that proceed at or below ambient temperature, without strong oxidants or acidic/basic additives. The key strategies involve optimizing catalyst properties, substrate modifications, and reaction partners to enhance mildness. Catalysts, particularly transition metals like Pd, Rh, Ir, and Ru, play a central role in C–H activation. For instance, Pd-based systems have shown success through the use of strongly electrophilic catalysts, such as Pd(OTf)₂, enabling room temperature reactions. Rh and Ir catalysts have also been optimized with electron-deficient ligands to improve reactivity and selectivity. The use of electron-rich ligands, such as N-heterocyclic carbenes (NHCs), has been crucial in enhancing the mildness of transformations. Rh-based systems, such as Cp*RhIII, have been modified with electron-deficient ligands to improve reactivity. Ir-based systems, like [Ir(dtbpy)(Bpin)₃], have demonstrated high efficiency in borylation reactions, even at low temperatures. Ru-based systems, such as RuH₂(CO)(PPh₃)₃, have been shown to activate C–H bonds under mild conditions, with the generation of active catalysts at high temperatures but efficient reactions at room temperature. Substrate modifications, such as the introduction of directing groups, have also been critical in improving the efficiency of C–H activation. These groups can enhance binding to the catalyst or facilitate subsequent functionalization steps. Additionally, the use of strongly coordinating ligands, such as phosphines and NHCs, has been shown to improve the reactivity and selectivity of transformations. The review also emphasizes the importance of understanding mechanistic aspects of C–H activation, including the role of different oxidation states and the influence of ligands on catalyst activity. The development of new catalysts and ligands has significantly advanced the field, enabling the synthesis of complex molecules with high efficiency and selectivity. Overall, the progress in mild C–H activation has made these reactions more practical and applicable in the synthesis of complex organic molecules.Mild metal-catalyzed C–H activation has emerged as a promising area in organic chemistry, offering efficient and selective transformations under mild conditions. This review highlights recent advancements in this field, focusing on reactions that proceed at or below ambient temperature, without strong oxidants or acidic/basic additives. The key strategies involve optimizing catalyst properties, substrate modifications, and reaction partners to enhance mildness. Catalysts, particularly transition metals like Pd, Rh, Ir, and Ru, play a central role in C–H activation. For instance, Pd-based systems have shown success through the use of strongly electrophilic catalysts, such as Pd(OTf)₂, enabling room temperature reactions. Rh and Ir catalysts have also been optimized with electron-deficient ligands to improve reactivity and selectivity. The use of electron-rich ligands, such as N-heterocyclic carbenes (NHCs), has been crucial in enhancing the mildness of transformations. Rh-based systems, such as Cp*RhIII, have been modified with electron-deficient ligands to improve reactivity. Ir-based systems, like [Ir(dtbpy)(Bpin)₃], have demonstrated high efficiency in borylation reactions, even at low temperatures. Ru-based systems, such as RuH₂(CO)(PPh₃)₃, have been shown to activate C–H bonds under mild conditions, with the generation of active catalysts at high temperatures but efficient reactions at room temperature. Substrate modifications, such as the introduction of directing groups, have also been critical in improving the efficiency of C–H activation. These groups can enhance binding to the catalyst or facilitate subsequent functionalization steps. Additionally, the use of strongly coordinating ligands, such as phosphines and NHCs, has been shown to improve the reactivity and selectivity of transformations. The review also emphasizes the importance of understanding mechanistic aspects of C–H activation, including the role of different oxidation states and the influence of ligands on catalyst activity. The development of new catalysts and ligands has significantly advanced the field, enabling the synthesis of complex molecules with high efficiency and selectivity. Overall, the progress in mild C–H activation has made these reactions more practical and applicable in the synthesis of complex organic molecules.