Hydrodynamic twisting enables bioinspired cellulose metafibers with exceptional strength and toughness.

Replacing high-performance synthetic fibers with sustainable bio-derived alternatives is critical for mitigating microplastic pollution but remains limited by the inferior mechanical performance of biomass-derived fibers. Here, we present bioinspired cellulose metafibers (Meta-CFs) enabled by a scalable hydrodynamic twisting strategy, wherein an asymmetric microfluidic field precisely guides the formation of continuously twisted architectures within a chemically cross-linked network, thereby locking in the ordered configuration and markedly suppressing defect accumulation. Multiscale experiments and simulations reveal that this strategy promotes efficient stress delocalization and cooperative load transfer. The resulting Meta-CFs achieve an unprecedented maximum tensile strength of 3.29 GPa (average 3.06 ± 0.23 GPa) and a toughness of 349.5 MJ m-3, simultaneously rivaling the strength of high-performance synthetic fibers and the toughness of natural spider silk. Furthermore, encapsulating multiple individual Meta-CFs with calcium alginate effectively scales up the bundle diameter while preserving GPa-level strength and full biodegradability. This upscaling strategy enables large-diameter structural applications, as demonstrated by durable trimmer lines that avoid the generation of persistent agricultural microplastic residues, thereby establishing a viable pathway toward high-performance, sustainable material alternatives.