Otsuki Fumihiko (?? ??, December 22, 1847 – February 17, 1928) was a Japanese lexicographer, linguist, and historian.
He is best known for two Japanese-language dictionaries that he edited, Genkai (??, "sea of words", 1891) and its successor Daigenkai (???, "great sea of words", 1932–1937), and for his studies of Japanese grammar.