The lack of an artificial system that mimics elemental sulfur (S8) oxidation by microorganisms inhibits a deep mechanistic understanding of the sulfur cycle in the biosphere and the metabolism of sulfur-oxidizing microorganisms. In this article, we present a biphasic system that mimics biochemical sulfur oxidation under ambient conditions using a liquid|liquid (L|L) electrochemical cell and gold nanoparticles (AuNPs) as an interfacial catalyst. The interface between two solvents of very different polarity is an ideal environment to oxidise S8, overcoming the incompatible solubilities of the hydrophobic reactants (O2 and S8) and hydrophilic products (H+, SO32–, SO42–, etc.). The interfacial AuNPs provide a catalytic surface onto which O2 and S8 can adsorb. Control over the driving force for the reaction is provided by polarizing the L|L interface externally and tuning the Fermi level of the interfacial AuNPs by the adsorption of aqueous anions.