<p>Transpiration cooling is a thermal management technique that utilizes the phase change of liquid coolant to effectively dissipate heat. Porous ceramic media play a crucial role in this cooling process by facilitating liquid transport and heat exchange; however, their intermittent capillary action and inter-grain phonon scattering significantly hinder rapid cooling. Here, we propose a strategy to create AlN-based nanofiber aerogel as a transpiration thermo-cooler, featuring vertically aligned channels and monocrystalline nanofibers by combining nanoengineering and multiscale structural assembly techniques. Benefiting from the unconstrained capillarity of aerogel channels, our thermo-coolers exhibit a fast liquid transport rate of up to 8.33 ± 0.026 mm s⁻¹, surpassing that of state-of-the-art porous media by one to two orders of magnitude. In addition, the enhanced phonon conduction properties of single-crystal AlN nanofibers enables thermo-coolers to achieve a fast cooling rate of 156.8 °C s⁻¹, outperforming advanced cooling materials by a factor of five and making them ideal for various thermal management applications.</p>