Two novel strains of thermophilic planctomycetes were recovered from terrestrial and subterranean habitats. Strain R1T was isolated from a hot spring (Kunashir Island, Russia) and strain SBP2T was isolated from a deep gold mine (South Africa). Both isolates grew in the temperature range 30–60 °C and pH range 5.0–8.0. Strain R1T grew optimally at 60 °C and pH 6.0–6.5; for SBP2T optimal conditions were at 52 °C and pH 7.5–8.0. Both strains were capable of anaerobic respiration with nitrate and nitrite as electron acceptors as well as of microaerobic growth. They also could grow by fermentation of mono-, di- and polysaccharides. Based on their phylogenetic position and phenotypic features we suggest that the new isolates represent two novel species belonging to a new genus in the order Planctomycetales , for which the names Thermogutta terrifontis gen. nov., sp. nov. and Thermogutta hypogea sp. nov. are proposed. The type strain of Thermogutta terrifontis, the type species of the genus, is R1T ( = DSM 26237T = VKM B-2805T), and the type strain of Thermogutta hypogea is SBP2T ( = JCM 19991T = VKM B-2782T).