UNIF 2017 will be the 31th in a series of annual international workshops on unification. Previous editions have taken place mostly in Europe (Austria, Denmark, France, Germany, Ireland, Italy, Poland, UK), but also in the USA and Japan. For more details on previous UNIF workshops, please see the UNIF homepage. Traditionally, the scope of the UNIF workshops has covered the topic of unification in a broad sense, encompassing also research in constraint solving, admissibility of inference rules, and applications such as type checking, query answering and cryptographic protocol analysis.