Ultralight ceramic aerogels are attractive thermal superinsulating materials, but display a formidable tradeoff between low and high temperature thermal conductivity (κ) due to their low-density features. Embedding carbon species as infrared opacifier in ultralight ceramic aerogels can substantially reduce the thermal radiation heat transfer without compromising the ultralow solid conduction. However, the oxidation resistance of embedded carbon species still remains inadequate to prevent thermal etching at high temperatures. Herein, we report a carbonaceous design and synthesis of ceramic nanofibrous aerogels with amorphous carbon embedded in the yttrium-stabilized zircon nanofibers to achieve a high-temperature thermal superinsulating performance with robust thermomechanical stability. The aerogels display one of the lowest κ of 95 mW·m⁻¹·K⁻¹ at 1,000 °C in air among ultralight material family, as well as robust mechanical flexibility with up to 95% compressive strain, 30% non-linear fracture strain, and 99% bending strain, and high thermal stability with ultralow strength degradation less than 1% after sharp thermal shocks (240 °C·s⁻¹) and working temperature up to 1,200 °C. The combined high-temperature thermal superinsulating and thermomechanical properties offer an attractive material system for robust thermal insulation under extreme conditions.