OII may refer to: Organisations OII, market exchange symbol for Oceaneering International Office of Innovation and Improvement, an office of the United States Department of Education Organisation Intersex International, a global advocacy and support group for people with intersex traits Oxford Internet Institute, a multi-disciplinary department, part of the University of Oxford, England See also Organisation Intersex International Australia OII Europe Oii-Chinese, the Chinese language affiliate of Organisation Intersex International