In the present study, chitin was extracted from marine crustacean shell waste (shrimp, crab, squilla and lobster) using traditional chemical methods (deproteinisation and demineralization) and its physicochemical and structural properties were characterized. The chitin content of crustacean shell waste ranged from 17.50% to 23.75% on a dry weight basis. The molecular weight analyses revealed that the crustacean chitin showed low molecular weight. The results of X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR), Energy dispersive X-ray analysis (EDAX), scanning electron microscopy (SEM) and thermogravimetry/differential thermal analysis (TG/DTA) confirmed that the α-chitins isolated from crustacean shell waste were similar to commercial crustacean chitin. The crystalline index value of the extracted chitin varied from 80.3% to 80.8%. The infrared spectroscopy analysis of the crustacean chitin exhibited two bands at around 1660 and 1620 cm⁻¹. SEM analysis of the extracted chitin showed the nanofibre and nanopore structures. Additionally, thermal stability of the crustacean chitin was close to that of the commercial chitin. Therefore, the results of this study confirmed that the extracted chitin is in α-form.