This book gathers a selection of peer-reviewed papers presented at the International Conference on Operations Research (OR 2018), which was held at the Free University of Brussels, Belgium on September 12 - 14, 2018, and was jointly organized by the German Operations Research Society (GOR) and the Belgian Operational Research Society (ORBEL). 575 scientists, practitioners and students from mathematics, computer science, business/economics and related fields attended the conference and presented more than 400 papers in parallel topic streams, as well as special award sessions. The respective papers discuss classical mathematical optimization, statistics and simulation techniques. These are complemented by computer science methods, and by tools for processing data, designing and implementing information systems. The book also examines recent advances in information technology, which allow big data volumes to be processed and enable real-time predictive and prescriptive business analytics to drive decisions and actions. Lastly, it includes problems modeled and treated while taking into account uncertainty, risk management, behavioral issues, etc.