<p>Nanocarriers are indispensable in biomedicine, enabling breakthroughs in drug delivery, vaccines and diagnostics. Despite notable successes facilitated by microfluidic technologies, sustainable, low-cost and high-throughput production of monodisperse nanocarriers remains a longstanding challenge. Here we report surfactant-flux-induced interfacial instability, a self-driven nanoemulsification mechanism triggered by non-equilibrium surfactant partitioning at a water–oil interface. This strategy produces 5 l of highly uniform nanoemulsion (0.2 l of disperse phase) in 1 min, producing droplets with diameters as small as 34 nm and polydispersity indices below 0.10. This self-driven nanoemulsification is robust across a broad range of pH values (~3–11) and temperatures (~4–85 °C), demonstrating compatibility with over ten oil–water–surfactant systems and enabling the synthesis of diverse nanocarriers including nanodroplets, micelles, vesicles, polymeric nanoparticles and metal–organic framework nanocrystals. We further demonstrate that surfactant flux underpins the observed interfacial instability, offering a mechanism for nanoemulsification under far-from-equilibrium conditions. This work addresses a bottleneck in nanomanufacturing and provides insights into dynamic surfactant behavior at immiscible interfaces.</p><p></p>