Anna Masterton Buchan was a Scottish novelist who wrote under the pen name O. Douglas. Most of her novels were written and set between the wars and portrayed small town or village life in southern Scotland, reflecting her own life.

William Sydney Porter, better known by his pen name O. Henry, was an American writer known primarily for his short stories, though he also wrote poetry and non-fiction. His works include "The Gift of the Magi", "The Duplicity of Hargraves", and "The Ransom of Red Chief", as well as the novel Cabbages and Kings. Porter's stories are known for their naturalist observations, witty narration, and surprise endings.

Octave Feuillet was a French novelist and dramatist. His work stands midway between the romanticists and the realists. He is renowned for his "distinguished and lucid portraiture of life", depictions of female characters, analyses of characters' psychologies and feelings, and his reserved but witty prose style. His most popular work remains his 1858 novel Le Roman d'un jeune homme pauvre, which has been adapted for film many times by Italian, French, and Argentinian directors.

Octave Mirbeau was a French novelist, art critic, travel writer, pamphleteer, journalist and playwright, who achieved celebrity in Europe and great success among the public, whilst still appealing to the literary and artistic avant-garde with highly transgressive novels that explored violence, abuse and psychological detachment. His work has been translated into 30 languages.

Octave Uzanne was a 19th-century French bibliophile, writer, publisher, and journalist.

Octavus Roy Cohen (1891–1959) was an early 20th-century American writer specializing in ethnic comedies. His dialect comedy stories about African Americans gained popularity after being published in the Saturday Evening Post and were adapted into a series of short films by Al Christie featuring actors Charles Olden, Spencer Williams Jr., Evelyn Preer, and Edward Thompson.

Olaudah Equiano, known for most of his life as Gustavus Vassa, was a writer and abolitionist from, according to his memoir, the village of Essaka in modern southern Nigeria. Enslaved as a child in Africa, he was shipped to the Caribbean and sold to a Royal Navy officer. He was sold twice more before purchasing his freedom in 1766.

Olive Higgins Prouty was an American novelist and poet, best known for her 1923 novel Stella Dallas and her pioneering consideration of psychotherapy in her 1941 novel Now, Voyager.

Olive Schreiner was a South African author, anti-war campaigner and intellectual. She is best remembered today for her novel The Story of an African Farm (1883), which has been highly acclaimed. It deals boldly with such contemporary issues as agnosticism, existential independence, individualism, the professional aspirations of women, and the elemental nature of life on the colonial frontier.

Olive Tilford Dargan was a writer and a poet. Her early works revolved around mountain poetry. Her works like: The Cycle's Rim, Lute and Furrow, Highland Annals were inspired from her love of mountains and nature. Later in her career, she published novels that focuses on racism, sexism, and fascism through her feminist visions of political activism and romanticism. Her most notable works were Call Home the Heart and A Stone Came Rolling which were written as part of her Gastonia novels.