This dataset compiles information on geothermal wells drilled into supercritical and near-supercritical conditions, with a focus on drilling and completion materials, fluid chemistry, and laboratory validation studies. The data are drawn from well reports, scientific literature, and laboratory testing programs and are organized into separate files by topic. All files are provided in CSV or Excel format with clearly labeled fields, and every record includes the columns well_name, geothermal_field, and country_region to allow cross-referencing across files. Source references are included in APA format within the data. The overview file provides general well information including location, depth, drilling year, temperature, pressure, and coordinates. The well component files (e.g., drill_bit, drilling fluids, cement, etc.) document materials used in drilling and completion, with fields for component type, material, specifications, issues observed, and references. The fluid chemistry file contains aqueous and vapor-phase geochemical measurements from selected geothermal wells and fields, including concentrations of major, minor, and trace elements as well as gas compositions. The material validation and testing file compiles laboratory results on the performance of metals, cement, proppants, lost circulation materials, and wellbore hydraulics under simulated supercritical geothermal conditions, with associated conditions, limitations, results, and recommendations. A README file is included to support dataset interpretation. It provides detailed descriptions of each file's structure, field definitions, unit conventions, and usage notes. Users are advised to consult the README to understand how to link well-level metadata across files and interpret measurement fields accurately. Some records may be incomplete or contain ranges and uncertainties as reported in the original sources. An associated paper summarizing this work and the broader project it is part of, including identified data gaps and recommendations, is linked below.