This book constitutes the refereed proceedings of the Forth Workshop onEngineering Applications, WEA 2017, held in Cartagena, Colombia, inSeptember 2017. The 59 revised full papers presented were carefully reviewed and selectedfrom156 submissions. The papers are organized in topical sections such as computerscience; computational intelligence; simulation systems; internet of things; fuzzy sets and systems; power systems; logistics and operations management; miscellaneous applications.