This is the peer reviewed version of the following article: Berumen, M. and Di Battista, J. and Rocha, L. 2017. Introduction to virtual issue on Red Sea and Western Indian Ocean biogeography. Journal of Biogeography. 44 (9): 1923–1926, which has been published in final form at 10.1111/jbi.13036 This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving at http://olabout.wiley.com/WileyCDA/Section/id-828039.html