Tamaki Saitō (斎藤 环, Saitō Tamaki; born September 24, 1961) is a Japanese psychologist and critic. He specializes in the psychiatry of puberty and adolescence. Saitō is Director of Medical Service at Sofukai Sasaki Hospital in Funabashi, Chiba. Saitō is notable for his study of hikikomori, a term he coined; he is internationally recognized as Japan's leading hikikomori expert. He is also known for presenting the theory of "multiple orientations" to explain otaku sexuality in Beautiful Fighting Girl. Since the 2010s, he has been involved in introducing Open Dialogue in Japan.