The 5th International Workshop on Elastic Networks Design and Optimisation (ELASTICNETS 2018 - Universitat Politècnica de València) is an open forum for discussion of research ideas about engineering of smart elastic networks capable of driving a future world strongly dependant on fog and cloud computing.  The workshop is open, free and it does not aim to be a forum of publication but a melting pot of research expertises for the creation of new networking paradigms. The workshop is funded by the Spanish Ministry of Economy and Competitivity (TEC2015-71932-REDT) and supported by Telefonica.