This book constitutes the refereed proceedings of the Forth Workshop on Engineering Applications, WEA 2017, held in Cartagena, Colombia, in September 2017.  The 59 revised full papers presented were carefully reviewed and selected from156 submissions. The papers are organized in topical sections such as computer science; computational intelligence; simulation systems; internet of things; fuzzy sets and systems; power systems; logistics and operations management; miscellaneous applications.  .