Ōi may refer to:
Japanese geography Ōi, Fukui Ōi, Kanagawa Ōi, Saitama Ōi District, Fukui Ōi River, Shizuoka Prefecture Ōi River (Kyoto Prefecture), part of the Katsura River
People with the surname Katsushika Ōi (c. 1800 – 1866), Japanese ukiyo-e artist , Japanese pool player
Other uses Grey-faced petrel, also known by its Māori name Ōi Ōi (shogi), one of the eight titles of Japanese professional shogi (board game) tournament Ōi Dam, Gifu Prefecture, Japan Japanese cruiser Ōi, a former cruiser in the Imperial Japanese Navy
See also Ooi – In some romanizations, ōi is sometimes written as ooi Oi (disambiguation)