Bioinspired Regenerative Lignification Enables Ultra‐Hard and Sustainable Bamboo Structural Materials

The pursuit of sustainable structural materials requires combining high performance with renewable resources and low environmental impact. Here, we introduce a bioinspired regenerative lignification strategy that reconstructs lignin‐like covalent networks directly within bamboo cell walls, condensing a multi‐year natural hardening process into hours. Unlike conventional delignification–densification or polymer‐filling approaches, this method preserves bamboo's hierarchical architecture while chemically stabilizing its matrix. The resulting ultra‐hard bamboo exhibits a tensile strength of 503 MPa and a Brinell hardness of 42.1 HB, with weight‐specific values surpassing steels and aluminum alloys. Multi‐scale analyses reveal that the synergistic effects of cell‐wall densification, enhanced cellulose crystallinity, and resin–cellulose cross‐linking drive the performance breakthrough. Beyond strength and hardness, the material demonstrates remarkable flame retardancy, fungal resistance, and dimensional stability in water. Techno‐economic and life‐cycle assessments confirm competitive costs and substantially lower carbon footprints compared with conventional structural metals and plastics. This scalable, nature‐inspired approach establishes a general pathway for transforming abundant biomass into next‐generation sustainable materials with performance exceeding traditional engineering alloys.