IOI may refer to:
Arts and entertainment Interonset interval, in music I.O.I, a South Korean girl group formed from the television show Produce 101 Innovative Online Industries (IOI), a fictional corporation in the 2011 novel Ready Player One Ready Player One (film), the 2018 film adaptation
Organisations International Ombudsman Institute, global organisation IOI Group, a Malaysian conglomerate IO Interactive, a Danish video game developer
Science and technology Idiopathic orbital inflammatory disease, involving any area of the orbit International Olympiad in Informatics, an annual competitive programming competition
Other uses Indication of interest, in financial trading Interest on investment or return on investment Island of Ireland, the geographical entity encompassing both the Republic of Ireland and Northern Ireland
See also LOL (disambiguation) 101 (disambiguation)