This data publication includes the IAGA-endorsed Kp index of geomagnetic activity as well as the derived indices ap, Ap, Cp and C9 in their definitive and nowcast version and the International Quiet and Disturbed Days. This dataset is provided by GFZ and derived from indices or near real-time geomagnetic observatory data provided by 13 contributing observatories. The Kp index and the derived products are distributed by GFZ and they are redistributed by various data centers and databases. When using the Kp index or any of the derived products of this dataset, please cite this data publication as well as the accompanying publication Matzka et al. (2021), which serves as a contemporary reference for users and describes the dataset and the state of the Kp index 70 years after its introduction.The Kp index The Kp index was introduced by Bartels (1949). We follow here generally the notation of Bartels (1957). A comprehensive list of references on the Kp index is provided in Matzka et al. (2021), which also describes the near real-time distribution of the indices. DOI and versioningWith the introduction of the DOI ‘https://doi.org/10.5880/Kp.0001’ for the dataset, the DOI landing page and the associated FTP server linked to this DOI become the dataset's primary archive (while the other established index distribution mechanisms at GFZ will be maintained in parallel). With the DOI, the dataset can grow with time, but a change of the data, once published, is not possible. If necessity arises in the future to correct already published values, then the corrected dataset will be published with a new DOI. Older DOIs and data sets will then still be available. For each DOI, an additional versioning mechanism will be available to document changes to the files such as format changes, which do not affect the integrity of the data. The DOI 10.5880/Kp.0001 identifies the current version.