<p>In this study, chitin and chitosan were isolated from the exoskeleton of freshwater crayfish (<i>Pontastacus leptodactylus)</i> collected from the Seyhan River and Eğirdir Lake, located in the Mediterranean region of Türkiye. The obtained chitosan materials were characterized using Fourier Transform Infrared Spectroscopy (FTIR) to define the functional components, Scanning Electron Microscopy (SEM) to analyze surface morphology, and X-ray Diffraction (XRD) to assess the mineral composition. The chitin and chitosan yields obtained from crayfish shells were determined as 48.11 ± 0.16% and 57.92 ± 0.05% for specimens collected from the Seyhan River, and 77.15 ± 0.1% and 80.33 ± 0.04% for specimens from Eğirdir Lake. The degrees of deacetylation (DD%) of the resulting chitosan biomaterials were 89.16% for the Seyhan River samples and 88.84% for the Eğirdir Lake samples. XRD analysis revealed that chitin and chitosan have crystalline structure. In addition, the surface morphology was examined in study and it was found that crayfish chitin exhibited a similar structure with a porous, rough and interwoven granular structure. It is noteworthy that the obtained chitin and chitosan materials have high yield ratios unlike previous studies. Moreover, this chitosan biomaterial with high DD% showed similar properties to commercial chitosan. Given that crayfish shells constitute approximately 50% of the total body weight, their accumulation is regarded as a substantial waste management concern. The transformation of these by-products into high value-added biomaterials, such as chitin and chitosan, is considered a viable approach for reducing organic waste loads within the framework of a circular bioeconomy. Accordingly, through the promotion of renewable resource valorization, this study underscores a pathway toward enhanced resource efficiency and potential economic benefits.</p> Graphical Abstract <p></p>