Sulfonyl hydrazides are stable and usually crystalline substances that can be accessed in a variety of ways, including transiently from hydrazones, to achieve a net reductive arylation of carbonyl compounds. We show their utility as versatile radical precursors, as exemplified with seven C-C bond-forming, redox-neutral cross-couplings with activated olefins, alkyl halides, redox-active esters, aryl halides, alkenyl halides, alkynyl halides, and a trifluoromethylating reagent, to forge C(sp3)-C(sp3), C(sp3)-C(sp2), and C(sp3)-C(sp) bonds. Exogenous redox (chemical, photo/electrochemical) additives are not necessary because these functional groups serve the dual role of radical precursor and electron donor. The homogeneous, water-compatible reaction conditions are operationally simple and contribute to streamlining synthesis and mild late-stage functionalization.