<p>Filamentous algae, characterized by high cellulose content and absence of lignin, present a promising sustainable alternative to conventional plant and synthetic fibers. The present study systematically evaluated the suitability of freshwater filamentous algae as a new resource for textile fibers, targeting applications in moisture-absorbent textiles. Among twelve strains screened, the isolate <i>Rhizoclonium</i> sp. emerged as the most promising candidate due to its high biomass yield (1.04&#xa0;g dry weight L^− 1) after 21 days of cultivation. In addition, it showed superior visible fiber flexibility following air-drying, an essential prerequisite for textile processing. Cultivation conditions were optimized (using WHM medium, pH 8, and thiamin supplementation) to maximize fiber quality, resulting in 8.6% increase in biomass productivity. Biochemical profiling of the optimized biomass revealed a significant enhancement of total carbohydrates (+ 18.0%), alongside reductions in protein (-18.4%) and ash content (-14.9%), supporting improved fiber durability and flexibility. Comparative FTIR analysis showed a strong cellulose signature and marked similarity to cotton, while also revealing high native starch content, further supporting their applicability as bio-based binders in nonwoven products. Functional characterization demonstrated that optimized <i>Rhizoclonium</i> sp. fibers exhibited exceptional moisture regain (~ 12%), surpassing conventional fibers such as cotton and lyocell. Overall, this study establishes native <i>Rhizoclonium</i> sp. as a highly versatile and renewable bioresource for innovative aquatic fibers, underpinning the development of an environmentally responsible algae-derived textile value chain.</p> Graphical Abstract <p></p>