On, on, or ON may refer to:

Arts and entertainment

Music

* On (band), a solo project of Ken Andrews * On (EP), ''On'' (EP), a 1993 EP by Aphex Twin * On (Echobelly album), ''On'' (Echobelly album), 1995 * On (Gary Glitter album), ''On'' (Gary Glitter album), 2001 * On (Imperial Teen album), ''On'' (Imperial Teen album), 2002 * On (Elisa album), ''On'' (Elisa album), 2006 * On (Jean album), ''On'' (Jean album), 2006 * On (Boom Boom Satellites album), ''On'' (Boom Boom Satellites album), 2006 * On (Tau album), ''On'' (Tau album), 2017 * On (song), "On" (song), a 2020 song by BTS * "On", a song by Bloc Party from the 2006 album ''A Weekend in the City''

Other media

* ''Ön'', a 1966 Swedish film * On (Japanese prosody), the counting of sound units in Japanese poetry * On (novel), ''On'' (novel), by Adam Roberts * ONdigital, a failed British digital television service, later called ITV Digital * Overmyer Network, a former US television network

Places

* On (Ancient Egypt), a Hebrew form of the ancient Egyptian name of Heliopolis * On, Wallonia, a district of the municipality of Marche-en-Famenne * Ahn, Luxembourg, known in Luxembourgish as ''On'' * Ontario, a Canadian province

Science, technology, and mathematics

Biology and medicine

* Operative note, documentation of care relating to an operation * Optic neuritis, especially relevant in multiple sclerosis * Osteonecrosis, death of bone tissue * Osteonectin, a glycoprotein

Other uses in science, technology, and mathematics

* ON Semiconductor, a semiconductor manufacturing company * O'Nan group, a mathematical group * OS/Net, the OpenSolaris Community * On, the proper class of all ordinal numbers

Other uses

* On (biblical figure), son of Peleth * On (company), a Swiss athletic shoe and sportswear company * On Kawara, Japanese artist * Nauru Airlines (IATA airline designator ON) * Leg side, in the game of cricket * Old Norse, a North Germanic language commonly referenced in etymology * Ontology, a branch of philosophy that deals with the concept of being * On'yomi, reading of Japanese kanji characters * Order of the Nation, a Jamaican honour * Overground Network, a railway scheme in South London * ON convoys, a series of WWII trade convoys * Orka náttúrunnar (ON Power), Icelandic geothermal power company