We determined the complete mitogenome of the oriental mayfly, Ephemera orientalis (Ephemeroptera: Ephemeridae) and the dragonfly Davidius lunatus (Odonata: Gomphidae). The 16,463-bp long E. orientalis and the 15,912 bp long D. lunatus mitogenome contains gene arrangement and content identical to the most common type found in a diverse insect order. Most individual E. orientalis and D. lunatus mt genes were well within the size found in the respective genes of other insects. The initiation codon for the D. lunatus COI gene was typical as ATA, whereas no typical start codon was found in the start region of E. orientalis COI gene. The A+T-rich regions of both mitogenomes have a few unusual feature. The A+T-rich region of E. orientalis contains a tandem repeat composed of two identical copies of 55 bp long, whereas that of D. lunatus contains a tandem repeat composed of duplicated identical 261-bp copies and one partial copy of the repeat. Also, the A+T-rich region of E. orientalis contains a single sequence and that of D. lunatus contains nine sequences, along with the tandem triplicate sequences, that has the potential to form stem-and-loop structures, flanked by the conserved sequences, “TA(A)TA” at the 5’ end and “G(A)nT’ at the 3’ end. Furthermore, the A+T-rich region of D. lunatus contains two tRNA-like structures, tRNALeu(UUR)-like sequence and tRNATyr-like sequence that have proper anticodon TAA and clover-leaf structure that were previously found in the hymenopteran insects.