The Heterotermitidae, or subterranean termites, is a family of termites that was elevated to family level from the subfamily Heterotermitinae, formerly nested in Rhinotermitidae. Recent cladistic analyses as of 2024 strongly support Heterotermitidae as sister to the Termitidae, forming the clade Geoisoptera. Members of this family are some of the most economically significant insects known, with Coptotermes formosanus in particular costing an estimated >$2.2 billion in damages within the United States alone. They primarily feed through the soil-wood interface, foraging for food through the soil and mud tubes. The nests of most species are typically diffuse galleries and tunnels, however Coptotermes is known to build more complex centralized nests built from carton, with some species building mounds.