An actinomycete strain was recovered from a pond where radon is known to be dissolved. A polyphasic study was undertaken to identify the new isolate. The 16S rRNA gene sequence of strain WA201(T) showed closest similarity to the type strains of Micromonospora carbonacea (98.5 %) and Micromonospora matsumotoense (98.1 %). The chemotaxonomic results confirmed the taxonomic position of the isolate in the genus Micromonospora. DNA-DNA relatedness values supported the classification of this isolate as a novel species. A number of physiological and biochemical tests were able to distinguish strain WA201(T) from its closest phylogenetic neighbours. Therefore, it is proposed that isolate WA201(T) (=DSM 44830(T)=LMG 22229(T)) be considered the type strain representing a novel species, Micromonospora mirobrigensis sp. nov.