Mitochondrial genomes are frequently used to infer phylogenetic relationships. Some taxa are, however, poorly represented. To facilitate better understanding of the potential of mitochondrial genome data in freshwater mussels, we present here, for the first time, the mitochondrial sequences of 4 complete F-type mitochondrial genomes from the European freshwater bivalve Unio pictorum (Unionidae). These genomes are very compact (15 761 bp) but have a typical gene complement for bilaterian mitochondrial genomes and a very similar organization to other unionid genomes available in databases. Very low nucleotide diversity within the species suggests a small effective population size of Polish U. pictorum, a phenomenon of potential importance for environmental management policies.