Background and Aims: Repeated cycles of demyelination and remyelination alter nerve tissue composition, likely affecting its material properties, including stiffness. Using ultrasound shear wave elastography (SWE), we assessed nerve shear wave velocity (SWV), a surrogate measure of stiffness, to determine its potential as a biomarker for demyelinating neuropathies, including chronic inflammatory demyelinating polyneuropathy, Charcot-Marie-Tooth type 1A, and anti-myelin-associated glycoprotein neuropathy. Methods: This cross-sectional study compared nerve SWV between 20 patients with demyelinating neuropathies (60.2 ± 13.1 years) and 16 age-matched controls (56.8 ± 10.8 years). Each participant underwent bilateral SWE of the proximal and distal segments of four peripheral nerves in the upper (median, ulnar and radial) and lower (sciatic-tibial) limbs. Measurements were conducted in different limb positions to mimic two nerve tensile states, yielding a total of 32 nerve stiffness measurements per participant. Conventional nerve cross-sectional area was further evaluated for each nerve and location. Results: Individuals with demyelinating polyneuropathy exhibited increased nerve SWV compared to age-matched controls (mean difference = 0.7 m/s, 95%CI [0.5 to 0.9]; p < 0.0001). This difference was observed across all nerves and regions, with the largest difference noted in the tibial. Axial nerve tension amplified these differences. Additionally, moderate to high negative correlations were observed between motor nerve conduction and nerve SWV. Interpretation: This study identifies significant neuropathy-associated alterations in peripheral nerve elasticity. Our findings suggest that nerve stiffness could be a promising biomarker for demyelinating neuropathies, and provide a basis for the development of standardized peripheral nerve SWE protocols.