A new iron-catalyzed cross-electrophile coupling reaction has been developed that couples benzyl halides with disulfides to form thioether products without the need for a terminal reductant or photoredox conditions. This method avoids sulfur-induced catalyst poisoning and the use of an exogenous base, offering broad scope and avoiding undesired elimination pathways. The reaction has been applied in various areas, including disulfide bioconjugation, drug synthesis, gram-scale synthesis, and product derivatization. Mechanistic studies suggest a stereoablative pathway involving oxidative cleavage between iron and the (pseudo)halide substrate, single electron steps, and an active thioether product. The reaction is efficient, scalable, and sustainable, utilizing iron as a cost-effective and non-toxic catalyst. The method provides a new approach for the synthesis of sulfur-containing molecules and offers advantages over traditional transition-metal catalysis. The reaction is also applicable for cleaving disulfide bonds in cystine derivatives, enabling new methods for peptide and protein labeling. The study highlights the potential of iron-catalyzed reactions in organic synthesis and bioconjugation.A new iron-catalyzed cross-electrophile coupling reaction has been developed that couples benzyl halides with disulfides to form thioether products without the need for a terminal reductant or photoredox conditions. This method avoids sulfur-induced catalyst poisoning and the use of an exogenous base, offering broad scope and avoiding undesired elimination pathways. The reaction has been applied in various areas, including disulfide bioconjugation, drug synthesis, gram-scale synthesis, and product derivatization. Mechanistic studies suggest a stereoablative pathway involving oxidative cleavage between iron and the (pseudo)halide substrate, single electron steps, and an active thioether product. The reaction is efficient, scalable, and sustainable, utilizing iron as a cost-effective and non-toxic catalyst. The method provides a new approach for the synthesis of sulfur-containing molecules and offers advantages over traditional transition-metal catalysis. The reaction is also applicable for cleaving disulfide bonds in cystine derivatives, enabling new methods for peptide and protein labeling. The study highlights the potential of iron-catalyzed reactions in organic synthesis and bioconjugation.