This book constitutes the refereed proceedings of the 30th International Conference, ISC High Performance 2015, [formerly known as the International Supercomputing Conference] held in Frankfurt, Germany, in July 2015.The 27 revised full papers presented together with 10 short papers were carefully reviewed and selected from 67 submissions. The papers cover the following topics: cost-efficient data centers, scalable applications, advances in algorithms, scientific libraries, programming models, architectures, performance models and analysis, automatic performance optimization, parallel I/O and energy efficiency.