O, or o, is the fifteenth letter of the English alphabet and the Latin script.

O may also refer to:

Letters , , letters in the Armenian alphabet , a letter in the Georgian alphabet Ο ο, Omicron, (Greek), a letter in the Greek alphabet, where Latin o is derived from O (Cyrillic), a letter of the Cyrillic alphabet O (kana), a romanization of the kana (お and オ) in Japanese writing , a consonant in Hangul, the Korean alphabet , a consonant in Burmese script

Arts and entertainment Film and television O (2001 film), a film starring Mekhi Phifer, Josh Hartnett, and Julia Stiles O (2022 film), an Indian Kannada-language horror thriller film

Literature O: A Presidential Novel, anonymous novel published in 2011 O, fictional planet that is the setting of several short stories by science fiction author Ursula K. Le Guin O, fictional character from the French erotic novel Story of O "O" Is for Outlaw, the fifteenth novel in Sue Grafton's "Alphabet mystery" series, published in 1999

Media and publications O, The Oprah Magazine, magazine founded by Oprah Winfrey O (German magazine), a fetish magazine

Music "O (Oh!)", 1920 by Ted Lewis, 1953 by Pee Wee Hunt O (A.C. Acoustics album), 2002 O (Damien Rice album), 2002 O (Eiko Shimamiya album), 2006 O (Omarion album), 2005 "O" (Omarion song), the title song O (Oval album), 2010 o (Tilly and the Wall album), 2008 O (EP), a 2023 EP by Yuju O, 2002 album by Zone "O", a 2014 song by Coldplay from Ghost Stories "o", a song by iamamiwhoami "O!", a song by the American band Bright from The Albatross Guest House, 1997 O (musician), nickname of the American musician Otis Barthoulameu A Band Called O

Sports O (gesture), a gesture used to show support for the sports teams of the University of Oregon Baltimore Orioles, an American Major League Baseball team, among whose common nicknames are "O's" and "The O's"

Others O (Cirque du Soleil), show at the Bellagio hotel and casino in Las Vegas, Nevada

Companies Essie's Original Hot Dog shop (commonly known as "The O"), a restaurant in Pittsburgh, Pennsylvania Overstock.com, online retailer previously known as O.co Realty Income, American real estate investment trust (NYSE stock ticker O)

History O-class battlecruiser, class of German ships in the 1930s The O (political group) (The Organization), a 1970s American political group

Linguistics /o/, close-mid back rounded vowel in the International Phonetic Alphabet O, an antiquated vocative placed before a name of, or phrase characterizing, the party being addressed O (also P), the patient-like argument (object) of a canonical transitive verb O, gender neutral third person pronoun in the Turkish language O-, an honorific prefix used in the Japanese language

Mathematics , a Bachmann–Landau notation in computational complexity theory ("|f| is bounded above by g asymptotically") , a Bachmann–Landau notation in computational complexity theory ("f is dominated by g asymptotically") O, for orthogonal group ∘ indicates function composition, or composition of morphisms in a category Category O or , a category of Lie algebra representations o, for octet, an information measure unit used in computing Kleene's O, a system of ordinal notations

Media O, an IRC operator service in QuakeNet's IRC services O Channel, the former name of Moji a television network in Indonesia

Places O Brook, a short river in Devon, England O'Block, a colloquial name for the Parkway Garden Homes in Chicago

Science Oxygen, symbol O, a chemical element O, a human blood type, the universal donor Haplogroup O (Y-DNA), a Y-chromosomal DNA haplogroup O, for pyrrolysine an alpha amino acid in biochemistry O-type star, stellar classification for very hot bluish stars O (for Octavius, meaning an eighth of a gallon), an apothecary's symbol for a pint

Surname O (surname), Korean surname romanized "O" or "Oh" Ō (Japanese surname), Japanese surname derived from the Chinese surname Wang (王) Ō clan a historical Japanese clan with an unrelated surname Ou (surname), Chinese and Cantonese surnames pronounced "O" or "Oh" A prefix meaning "grandson (of)", appearing in Irish surnames Genovevo de la O (1876–1952), Mexican revolutionary Karen O, born Karen Lee Orzolek, American singer

Other uses Oreo O's, an American breakfast cereal available internationally Oscar, the military time zone code for UTC−02:00: List of military time zones#O , the official West Japan Railway Company service symbol for the Osaka Loop Line O, a handwritten symbol for a hug

See also

Mr. O (TV show) Circle (disambiguation) Circle symbol (disambiguation) Zero (disambiguation) Big O (disambiguation) Oh (disambiguation) Omicron (disambiguation) including Ο/ο