Penny O'Connor trained and worked as an actor before becoming a full-time teacher of the Alexander Technique in 1992. She has taught at several London drama schools including ArtsEd, where she was resident for eighteen years, and is a member of the Society of Teachers of the Alexander Technique.

Ronan O'Donnell is a playwright based in Scotland whose work has been staged by the Traverse Theatre, LLT and Arches/Theatre of Imagination, amongst others.

John O'Donovan is a London-based playwright from Co. Clare, Ireland. His plays include Flights (Clapham Omnibus, 2020), Sink (Dublin Fringe Festival, 2019) and If We Got Some More Cocaine I Could Show You How I Love You (Old Red Lion, London, 2016).

Robert O'Hara is an African-American playwright and director. His play Antebellum received a world premiere production from Woolly Mammoth Theater Company, and earned him a Helen Hayes Award for Outstanding New Play. He reworked The Wiz for its revival at La Jolla Playhouse. He wrote and directed the world premiere of Insurrection: Holding History (Public Theater, Oppenheimer Award for Best New American Play). As a director, he has won an Obie Award and an NAACP Best Director Award and has worked at acclaimed theaters throughout the United States.

Jeanie O'Hare is a short-story writer, playwright and project consultant for theatre and film. She originally trained as a sculptor. She has worked for the Royal Court Theatre, the Royal Shakespeare Company, Druid Theatre, and was Chair of Playwriting at Yale School of Drama. Most recently she was the Director of New Work Development at the Public Theater in New York. Her focus is on scouting, developing and producing new writers who tell original and important stories.

John O'Neal co-founded the Free Southern Theater in 1963 as a cultural arm of the southern Civil Rights movement, and later founded Junebug Productions, a professional African-American arts organization in New Orleans.

For FST, O'Neal worked as a field director for the Student Nonviolent Coordinating Committee and worked as national field program director with the Committee for Racial Justice.

He has written eighteen plays, a musical comedy, poetry, and several essays, and has performed throughout the United States, Canada, France, and Scandinavia. He is the recipient of the Award of Merit from the Association of Performing Arts Presenters, the United States Artists Award, and a Ford Foundation Award.

Cordelia O'Neill is an actor and writer, and a founding member of The Small Things Theatre Company.

Her plays include: Anything is Possible if You Think About It Hard Enough (VAULT Festival, 2018; Southwark Playhouse, London, 2021; winner Best New Play at the 2022 Offies (Off West End Awards)); No Place for a Woman (Theatre503, London, 2017); and The Stolen Inches (Edinburgh Festival Fringe, 2015).

Eugene O'Neill was the first American dramatist to win the Nobel Prize for Literature, and at the time of his death in 1951 had written over twenty plays.

Jody O'Neill is an actor and writer.

Her plays include What I (Don't) Know About Autism (Abbey Theatre, Dublin, 2020) and Bailybaile, which won a Commendation at the 2019 Bruntwood Prize for Playwriting.