Despite the extensive investigation on solid‐state lithium‐metal batteries (SSLMBs), their application in flexible electronic devices has been plagued mainly by the physicochemical/mechanical instability of their electrode–electrolyte interfaces. Here, we present a fibrous skeleton‐framed, quasi‐solid‐state LMB (fs‐QSSLMB) as a new cell architecture concept to simultaneously achieve the high‐energy‐density, mechanical flexibility, and safety. The fs‐QSSLMB is fabricated by embedding poly(ethylene terephthalate) (PET) nonwovens, stainless‐steel meshes, and metal‐coated conductive PET nonwovens with a lithiophilic‐gradient morphology as customized fibrous skeletons into quasi‐solid‐state electrolytes (QSSEs), high‐capacity LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes, and Li metal anodes, respectively. The stepwise printing of the NCM811 cathode/QSSE/Li anode assembly and the subsequent one‐pot ultraviolet curing of the gel electrolyte precursors in the assembly enable the formation of seamless interfaces between the electrodes and QSSE, thereby ensuring the electrochemical sustainability and mechanical deformability of the fs‐QSSLMB. In addition, owing to its fibrous skeleton‐based structural uniqueness and seamless interfaces, the fs‐QSSLMB exhibits electrochemical reliability, mechanical flexibility, safety (i.e., electrochemically active after being vertically cut in half and exposed to flame), and high (cell‐based) gravimetric/volumetric energy densities (385 Wh kgcell−1/451 Wh Lcell−1).