The radical-mediated C–H functionalization of pyridines, catalyzed by visible light, has emerged as a powerful and versatile strategy in organic chemistry. This approach enables direct and selective modification of the pyridine framework, significantly expanding the toolkit available for organic synthesis. In recent years, N-functionalized pyridinium salts have gained considerable attention in this field, serving dual roles as both radical precursors and pyridine surrogates. N-functionalized pyridinium salts offer several key advantages over traditional pyridine reactants. They enhance reactivity and selectivity in synthetically valuable transformations; perform excellently under mild, acid-free conditions; and provide superior regiocontrol for nontraditional Minisci-type reactions. These properties have made them increasingly valuable in modern organic synthesis, particularly in the context of late-stage functionalization and complex molecule synthesis. Recent advancements in this area have been substantial and diverse. Researchers have developed a wide array of synthetic applications using pyridinium salts under visible-light conditions, ranging from C–H functionalization to heterocycle formation. Notably, N-substituted pyridinium salts have been ingeniously utilized as bifunctional reagents for alkene difunctionalization, opening new avenues for molecular complexity generation. Innovative approaches involving light-absorbing electron donor-acceptor (EDA) complexes between pyridinium salts and electron-rich donors have been introduced, enabling new reactivity patterns in photocatalyst-free conditions. This strategy not only simplifies reaction setups but also expands the scope of accessible transformations. Furthermore, the establishment of enantioselective reactions using pyridinium salts represents a significant breakthrough, further broadening their synthetic utility and addressing long-standing challenges in asymmetric synthesis. These developments collectively demonstrate the versatility and potential of N-functionalized pyridinium salts in advancing the frontiers of organic synthesis. This comprehensive chapter provides an in-depth overview of these developments, meticulously organized based on the N-substituent of pyridinium salts and their distinct reactivity patterns. It delves into recent advancements in N-functionalized pyridinium salt chemistry, discussing a wide range of organic reactions utilizing these compounds under visible-light conditions. The authors explore crucial structure-reactivity relationships based on N-substituents as well as innovative activation modes and their mechanistic implications, providing insights that are vital for reaction design and optimization.