OO

OO, O_O or variants may refer to:

Arts and entertainment

 * OO (EP), by Zion.T, 2017
 * OO, production code for the 1967 Doctor Who serial The Ice Warriors
 * "O.O" (song), by Nmixx, 2022

Places

 * Oô, France
 * Oo, Indonesia

Science and transportation

 * Ōō, an extinct bird of the genus Moho
 * SkyWest Airlines, IATA airline code OO
 * OO, the aircraft registration prefix for Belgium
 * Old Oak Common TMD, England, carriage shed depot code OO

Other uses

 * several emoticons
 * , a Latin-script digraph
 * Ꝏ, a ligature of the Latin script.
 * Oo stick, a traditional Hawaiian digging bar
 * Original Oratory, a competitive event in high school forensic competitions
 * OO gauge, a model railway standard
 * Official Observer, an appointed amateur radio operator
 * Oo Zun (1868–1944), Burmese social worker and Buddhist nun
 * Tin Oo (1927–2024), Burmese politician, activist and military