A new species, Olopachys iraniensis n. sp. (Mesostigmata: Pachylaelapidae) is described based on adult females collected from soil in Guilan Province, northern Iran. Two identification keys are provided, one for all known species of Olopachys, and the other for species recorded from Iran. A brief review on pachylaelapid mites of Iran is also provided. Keywords Acari; Olopachys; Pachylaelapidae; new species; soil; Guilan Zoobank http://zoobank.org/7D80D390-FE33-46A5-B60C-D37C36D61A6D How to cite this article Mojahed S. et al. (2019), A new species of Olopachys Berlese (Acari: Pachylaelapidae) from Iran with a key to the world species.