Description: KTB Borehole Measurements Data Magnetic Susceptibility and Magnetic Field Extensive borehole measurements were performed during the active drilling phase of the KTB pilot and main hole. The data report STR 21/03 KTB Borehole logging data contains the full description of the logging data given here. Please read it thoroughly to avoid inappropriate or wrong use of the data. The KTB borehole measurement data files contain the final processed versions of logging data from the two KTB boreholes: • KTB-Oberpfalz VB (KTB Vorbohrung/Pilot Hole or KTB-VB) • KTB-Oberpfalz HB (KTB Hauptbohrung/Main Hole or KTB-HB). Here only the acronyms KTB-VB and KTB-HB are used. In total there are 145 data files from the KTB-VB and 239 data files from the KTB-HB. All logs were run in open hole unless noted otherwise (see the file header). The maximum logging depth was 4001 m in the KTB-VB and 9085 m in the KTB-HB. The Magnetic Susceptibility (MSUS) and Magnetic Field data files comprise data from a magnetic susceptibility sonde from the university of Munich, and two magnetometer sondes from the university of Braunschweig (FML-BS) and of Schlumberger (GPIT). MSUS was only run in the KTB-VB. The Braunschweig magnetometer was run in both KTB boreholes and the GPIT only in the KTB-HB. The MSUS log and the magnetic field log in the KTB-VB are not depth corrected to the reference GR because the sondes had no GR sensor. Both types of magnetic field logs in the KTB-HB are depth corrected to the reference GR. The data are provided in ASCII format. Detailed descriptions are provided in the associated data report (STR 21/03, Kueck et al., 2021) and the KTB Borehole Measurements Catalog. Acknkowledgements: The GFZ German Research Centre for Geosciences, Potsdam, Germany, as successor of the KTB Project Management provides the logging data, which were obtained under grants RG8604, RG8803 and RG 9001 of the Federal Ministry of Research and Technology of Germany.