The development of lightweight, strong and high-performance thermal insulators from renewable biomass are highly desired for sustainable development. Here, ultralight aerogels based on renewable nanochitin with outstanding mechanical properties, excellent water-resistant, and promising thermal insulation properties are fabricated. The pristine nanochitin aerogels (PNCAs) assembled from mechanically strong carboxylated chitin nanorods are firstly prepared through acid-induced gelation and supercritical drying. The resultant PNCAs present tunable density (10−50 mg/cm 3 ) and strong mechanical stiffness (the specific compression modulus of 30.2 MPa cm 3 /g) combining with low thermal conductivity (27.2 mW/m K). After a facile silylation mod-ification, the silylated nanochitin aerogels (SNCAs) exhibit hydrophobic behavior (contact angle > 130°), im-proved compression performance (the specific compression modulus of 65 MPa cm 3 /g), and promising thermal insulation property (30.5–35.8 mW/m K). Moreover, the silylated aerogel shows a negligible loss of mechanical performance when exposed to water for 12 h at 35 °C.