This book constitutes the proceedings of the workshops and associated events that were held in conjunction with the 31st European Conference on Parallel and Distributed Processing, Euro-Par 2025, which took place in Dresden, Germany, during August 25–29, 2025.The 40 full workshops papers included in these proceedings were carefully reviewed and selected from a total of 69 submissions.They stem from the following workshops: 10 papers from HETEROPAR 2025, 8 papers from PECS 2025, 5 papers from HiPES-TA 2025, 5 papers from DYNRESHPC 2025, 5 papers from WSCC 2025, 4 papers from GraphSys 2025 and 3 papers from VHPC 2025.The books also contains 8 Demo/Poster papers accepted from 10 submissions to this track; the Euro-Par PhD Symposium received 15 submissions from which 11 papers have been accepted for publication; for the Euro-Par Women in HPC track a total of 4 papers has been accepted.