Hideki Imai (今井 秀樹, Imai Hideki, born 1943 in Shimane Prefecture, Japan) is an information theorist and cryptographer, currently the director of Research Center for Information Security (RCIS), National Institute of Advanced Industrial Science and Technology (AIST) and a full professor at Chuo University. His notable work includes research in coding theory, block cipher design, and public-key cryptography.In 1977, together with Hirakawa, he proposed a coded multilevel signal modulation scheme.