We describe the initial sequencing and assembly of the complete mitochondrial genome of
Appasus japonicus
Vuillefroy, 1864 (Hemiptera; Belostomatidae; Appasus). The mitochondrial genome of
A. japonicus
was found to be 18,608 bp. It contains thirteen protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), two ribosomal RNAs (rRNAs) and an AT-rich region. The overall base composition of
A. japonicus
is A-41.9%, C-17.5%, G-11.9%, and T-28.7%. A phylogenetic analysis of 21 species within the order Hemiptera suggests that
Diplonychus rusticus
is most closely related to
A. japonicus
.