Samia ricini, a gigantic saturniid moth, has the potential to be a novel lepidopteran model species. Since S. ricini is much more tough and resistant to diseases than the current model species Bombyx mori, the former can be easily reared compared to the latter. In addition, genetic resources available for S. ricini rival or even exceed those for B. mori: at least 26 eco-races of S. ricini are reported and S. ricini can hybridise with wild Samia species, which are distributed throughout Asian countries, and produce fertile progenies. Physiological traits such as food preference, integument colour, larval spot pattern, etc. are different between S. ricini and wild Samia species so that those traits can be the target for forward genetic analysis. In order to facilitate genetic research in S. ricini, we determined the whole genome sequence of S. ricini. The assembled genome of S. ricini was 458 Mb with 155 scaffolds, and the N50 length of the assembly was approximately 21 Mb. 16,702 protein coding genes were predicted in the assembly. Although the gene repertoire of S. ricini was not so different from that of B. mori, some genes, such as chorion genes and fibroin genes, seemed to have specifically evolved in S. ricini.