This collection of papers presents a systematic and representative vision of the current status of the art on magneto-rheological fluids (MRFs), including their classical and novel applications. Each topic is presented with a rich and updated bibliography, helping readers to further deepen their knowledge of the matter. This reprint presents international contributions from researchers in many countries in Europe and Asia. The Editors are senior researchers at the Italian Aerospace Research Centre and the University of Naples Federico II in Italy, and at the Polymer Competence Center in Leoben, Austria.