Molecular design combining biobased feedstocks, fiber processability, and reversible crosslinking is important for sustainable textiles. Herein, we report a new molecular design and synthetic strategy for partially biobased polyurethanes with tuneable chemical composition and properties, which show potential for the development of reversibly crosslinked textile fibers with enhanced recyclability. A lignin-derived new aromatic monomer was synthesized as the rigid building block, which could be copolymerized with flexible tetraethylene glycol and diisocyanates to achieve the balanced structural rigidity needed for fiber design. Moreover, a sugar-based 2,5-bis(hydroxymethyl)furan was also incorporated in the copolymerization, which offers enhanced structural rigidity and enables thermally induced crosslinking/decrosslinking based on Diels-Alder chemistry. The resulting polyurethanes exhibited moderate to high molecular weights (10–280 kDa) and tuneable glass transition temperatures (31–124°C). Reversible crosslinking/decrosslinking of the obtained polymers could be conveniently carried out and repeated at least five cycles without significant property deterioration. Selected polymers were processed into noncrosslinked and crosslinked fibers by wet spinning at different draw ratios. The spinnability, thermal properties, and fiber mechanical responses were affected by molecular composition and processing conditions. These results demonstrate that the molecular design strategy successfully introduces thermally reversible crosslinks into partially biobased polyurethanes with potential for fiber applications