High‐performance thermal insulating aerogels are attractive candidates for thermal protection in extreme environments. However, inorganic aerogels’ brittleness and poor machinability limit their applications, while organic aerogels suffer from severe strength degradation and structural collapse at high temperatures. Herein, for the first time, a thermo‐responsive self‐ceramifiable aerogel is demonstrated with exceptional strengthening and thermal insulation at high temperatures. This aerogel exhibits excellent toughness and processability like polymers under normal conditions but spontaneously transforms into high‐strength semi‐crystalline hard ceramics upon exposure to high temperatures. After prolonged thermal attack at 800 °C, the strength of the aerogels does not decrease but significantly increases several‐fold (from 0.739 to 2.726 MPa). The self‐ceramization behavior and mechanism of the aerogel are illustrated in detail. The unique self‐ceramifiable capacity enables aerogels to provide fire resistance, high‐strength support, and excellent thermal insulation at ultrahigh temperatures. Even with continuous burning at 1300 °C for 60 min, the 15 mm thick aerogel shows low backside temperature below 300 °C, crack‐free overall structure, and invariant porous morphology. This self‐ceramifiable aerogel opens up a new avenue for developing thermal‐protection materials with toughness, machinability, high strength, and thermal insulation in extreme environments. A new thermo‐responsive self‐ceramifiable aerogel is for the first time reported with exceptional strengthening and thermal insulation at high temperatures. Under normal conditions, the aerogel exhibits excellent toughness and machinability. Upon exposure to high temperatures, the aerogel spontaneously and rapidly transforms into robust semi‐crystalline hard ceramics, thus leading to fire resistance, high strength, and thermal insulation in extreme environments.