Machine Learning Summer School on Reliability & Safety (MLSSR&S 2026) is a five-day summer school dedicated to selected topics in machine learning, with a focus on AI safety, reliability and robustness of machine learning systems. The school is organised as an intensive academic programme built around invited lectures delivered by a carefully selected group of researchers from academia and industry, whose work has significantly contributed to the development of the field. Speakers are actively involved in current research and are invited based on their scientific contributions and expertise. The school is co-organised by Jagiellonian University, GMUM – Group of Machine Learning Research, ML in PL, IDEAS Research Institute and ELLIS Unit Warsaw.