Oin

Oin, Óin or OIN may refer to:

Folklore and fiction

 * Óin, son of Gróin, a Dwarf from J. R. R. Tolkien's writings, companion of Thorin Oakenshield
 * Oin-Oin, a character of Swiss folklore

Other

 * Open Invention Network, a company specialising in patent with Linux
 * Oneida Indian Nation, the New York tribe that operates Turning Stone Resort & Casino
 * One language, specifically Inebu, by ISO 639-3 code