The 9th International Conference on Cloud Computing and Services Science, CLOSER 2019, focuses on the emerging area of Cloud Computing, inspired by some latest advances that concern the infrastructure, operations, and available services through the global network. Further, the conference considers as essential the link to Services Science, acknowledging the service-orientation in most current IT-driven collaborations. The conference is nevertheless not about the union of these two (already broad) fields, but about Cloud Computing where we are also interested in how Services Science can provide theory, methods and techniques to design, analyze, manage, market and study various aspects of Cloud Computing.