We demonstrate threshold switching behaviors with working temperatures up to 500 °C based on GaN vertical p-n diodes, and these devices survived a passive test in a simulated Venus environment (460 °C, 94 bar, CO2 gas flow) for ten days. This is realized via interface engineering through an etch-then-regrow process combination with a Ga2O3 interlayer. It is hypothesized the traps in the interfacial layer can form/rupture a conductive path by trapping/detrapping electrons/holes, which are responsible for the observed threshold switching behaviors. To the best of our knowledge, this is the first demonstration of two-terminal threshold-switching memory devices under such high temperatures. These results can serve as a critical reference for the future development of GaN-based memory devices for harsh environment applications.