This book constitutes the refereed proceedings of the 10th International Workshop on Simulation and Synthesis in Medical Imaging, SASHIMI 2025, held in conjunction with the 28th International conference on Medical Image Computing and Computer Assisted Intervention, MICCAI 2025, in Daejeon, South Korea, on September 23, 2025.The  17 papers included in this book were carefully reviewed and selected from 25 submissions. They focus on wide range of topics relevant to SASHIMI and reflect recent developments in methods for image-to-image translation, generative modelling, physics-inspired synthesis, super-resolution and image segmentation and classification.Applications include magnetic resonance imaging (MRI), computed tomography (CT), optical coherence tomography (OCT) and histopathology imaging.