Clunio marinus is an emerging model system for the study of circadian and circalunar clocks, as well as the evolutionary mechanisms for local adaptation. We sequenced, assembled, annotated and genetically mapped a Clunio marinus reference genome. The three chromosomes are fully reconstructed, enabling genome-wide synteny comparisons and detection of large-scale structural variation. We also re-sequenced pools of five Clunio marinus populations that differ in circadian and circalunar timing, which allowed to detect genetic variation associated with timing differences.