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Here we report on the high-temperature piezoresistivity of carbon-containing silicon oxycarbide nanocomposites (C / SiOC). Samples containing 13.5 vol% segregated carbon have been prepared from a polysilsesquioxane via thermal cross-linking, pyrolysis and subsequent hot-pressing. Their electrical resistance was assessed as a function of the mechanical load (1&ndash;10 MPa) and temperature (1000&ndash;1200 &deg;C). The piezoresistive behavior of the C / SiOC nanocomposites relies on the presence of dispersed nanocrystalline graphite with a lateral size &le; 2 nm and non-crystalline carbon domains, as revealed by Raman spectroscopy. In comparison to highly ordered carbon (graphene, HOPG), C / SiOC exhibits strongly enhanced <i>k</i> factor values, even upon operation at temperatures beyond 1000 &deg;C. The measured <i>k</i> values of about 80 &plusmn; 20 at the highest temperature reading (<i>T</i> = 1200 &deg;C) reveal that C / SiOC is a primary candidate for high-temperature piezoresistive sensors with high sensitivity.