Nuphar saikokuensis is a species of rhizomatous aquatic plant endemic to Japan.

[1] Nuphar saikokuensis is an aquatic perennial herb with prostrate, branching rhizomes.

[2] The yellow, protogynous, pedunculate, 3–4 cm wide flowers are raised above the water surface.

[1] The type specimen was collected by T. Shiga in Oda-cho, Ono-shi, Hyogo prefecture, Japan on the 30th of May 2001.

[2] The specific epithet saikokuensis is derived from the Japanese regional name "Saikoku", meaning Western Japan, to which this species is native to.