In this paper we introduce Besov-Morrey spaces with all indices variable and study some fundamental properties. This includes a description in terms of Peetre maximal functions and atomic and molecular decompositions. This new scale of nonstandard function spaces requires the introduction of variable exponent mixed Morreysequence spaces, which in turn are defined within the framework of semimodular spaces. In particular, we obtain a convolution inequality involving special radial kernels, which proves to be a key tool in this work.Date: April 15, 2019. 2010 Mathematics Subject Classification. 46E35, 46E30, 42B25.