This book constitutes the refereed proceedings of the 11th International Conference on Optimization and Applications, OPTIMA 2020, held in September - October 2020. Due to the COVID-19 pandemic the conference was held online.  The 18 revised full papers presented were carefully reviewed and selected from 60 submissions. The papers are organized in topical sections on global optimization; combinatorial and discrete optimization; optimal control; optimization in economy, finance and social sciences; applications.