The article discusses the development and application of bidentate, monoanionic auxiliaries in transition-metal-catalyzed carbon–hydrogen (C–H) bond functionalization. This methodology has evolved from an organometallic curiosity to a mainstream technique in the synthesis of complex natural products and drugs. C–H bonds are abundant in organic molecules, making their functionalization advantageous as it shortens synthetic pathways and reduces reagents, solvents, and labor. The use of bidentate, monoanionic directing groups has enabled the functionalization of both activated and unactivated C–H bonds, particularly in palladium-catalyzed reactions. These auxiliaries, such as aminoquinoline and picolinic acid, are versatile and can be removed after reaction, enabling their use in the synthesis of natural products and medicinally relevant compounds. The article also covers the use of these auxiliaries in copper-catalyzed functionalization of sp² C–H bonds, including sulfenylation, amination, etherification, and fluorination. Additionally, cobalt-catalyzed functionalization of sp² and sp³ C–H bonds is discussed, highlighting the efficiency of these methods. The versatility of these auxiliaries is attributed to their ability to stabilize high oxidation states of transition metals, facilitating C–H bond functionalization. However, the use of expensive second-row transition metals remains a limitation for sp³ C–H bond functionalization. The development of these directing groups represents a significant advance in C–H bond functionalization chemistry, offering a general and efficient approach for synthetic applications. The article also highlights the potential for further improvements, such as the use of first-row transition metals and simpler directing groups for more efficient functionalization of unactivated C–H bonds.The article discusses the development and application of bidentate, monoanionic auxiliaries in transition-metal-catalyzed carbon–hydrogen (C–H) bond functionalization. This methodology has evolved from an organometallic curiosity to a mainstream technique in the synthesis of complex natural products and drugs. C–H bonds are abundant in organic molecules, making their functionalization advantageous as it shortens synthetic pathways and reduces reagents, solvents, and labor. The use of bidentate, monoanionic directing groups has enabled the functionalization of both activated and unactivated C–H bonds, particularly in palladium-catalyzed reactions. These auxiliaries, such as aminoquinoline and picolinic acid, are versatile and can be removed after reaction, enabling their use in the synthesis of natural products and medicinally relevant compounds. The article also covers the use of these auxiliaries in copper-catalyzed functionalization of sp² C–H bonds, including sulfenylation, amination, etherification, and fluorination. Additionally, cobalt-catalyzed functionalization of sp² and sp³ C–H bonds is discussed, highlighting the efficiency of these methods. The versatility of these auxiliaries is attributed to their ability to stabilize high oxidation states of transition metals, facilitating C–H bond functionalization. However, the use of expensive second-row transition metals remains a limitation for sp³ C–H bond functionalization. The development of these directing groups represents a significant advance in C–H bond functionalization chemistry, offering a general and efficient approach for synthetic applications. The article also highlights the potential for further improvements, such as the use of first-row transition metals and simpler directing groups for more efficient functionalization of unactivated C–H bonds.