Continuing the series of conferences established in 1993, the 15th German Probability and Statistics Days (GPSD) 2021 are taking place "in" Mannheim from September 27th to October 1st 2021. The GPSD conferences are organized biannually with the support of the DMV-Fachgruppe Stochastik e.V. The series of conferences provides an important forum for presenting and discussing the latest developments in the field for both young and senior researchers in Germany, Europe and beyond. In 14 specialized sections on probability, statistics and their applications in physics, biology, finance, insurance and data science researchers discuss contributed prerecorded and invited live talks. A virtual social event and further interactions will offer opportunities to have informal discussions and meet new colleagues.