<p>Methanogenesis was previously considered to be strictly confined to anoxic environments, but aerobic methane (CH₄) production is increasingly being recognized, although it is typically ascribed to biological activity or photothermal reactions. Here we describe rhizosphere soil incubation experiments and biogeochemical analyses and our findings that photothermally inert rhizospheres of aquatic plants sustain widespread oxic CH₄ formation in the absence of microbial CH₄ oxidation. Circadian radial oxygen loss from plant roots induces redox oscillations in the rhizosphere that drive the CH₄ production. At night, iron minerals in the soil are reduced, and during the day, the Fe(II) produced overnight is re-oxidized. This sequence generates reactive oxygen species and oxo–iron(IV) complexes, which mediate demethylation of organic substrates and release CH₄ as a by-product. The extent of this redox-driven CH₄ formation depends largely on the soil iron reactivity and the composition of the organic matter. Using a random forest model, we estimate that the global CH₄ production potential in rice rhizospheres is on the order of 0.7–3.3 Tg yr⁻¹, corresponding to 1.9–13.2% of total paddy CH₄ emissions. These findings uncover a redox-driven CH₄ source, with implications for global CH₄ budgets and organic carbon cycling.</p>