Born in Cork, Ireland to poet and novelist Robert Anthony Welch, O'Riordan first trained as a ballet dancer. This rigorous grounding began as a 6-year-old and culminated in a scholarship to the White Lodge, Royal Ballet School and then Mariinsky Ballet (formerly Kirov). She then studied English and Theatre studies at Queen Mary, University of London before completing her phD entitled Shakespeare's Physical Texts at the University of Ulster.
Spending most of her twenties as a choreographer and movement director, from to 2002 to 2011 O'Riordan co-founded and ran the Ransom theatre company in Belfast, Northern Ireland, where she notably directed the production Hurricane, which starred Richard Dormer and told the story of snooker legend Alex Higgins. The show was a hit at the Edinburgh Festival Fringe and received almost universally positive criticism earning it a season in London's west-end and off Broadway in New York. The success of Hurricane secured Rachel a season with the Peter Hall Company Theatre company where she directed August Strindberg's play, Miss Julie, and an adaption of George Orwell's Animal Farm at the Theatre Royal in Bath, England.
O'Riordan's tenure as artistic director of Ransom saw her commission and direct various new works, including the first play by David Ireland, Arguments for Terrorism, and new plays by Leo Butler and Suzie Miller, Protestants, and the Irish famine-based This Piece of Earth. During this time she also ran a three year programme entitled Writers on the Edge to develop new writing for women in Northern Ireland where she worked closely with Paines Plough and the Soho Theatre.
O'Riordan was Artistic Director at the Perth Theatre between 2011 and 2014. Her first production was William Shakespeare's Twelfth Night. In October 2013 the Chair of the Board of Trustees of Sherman Theatre Cymru, David Stacey announced that Rachel O’Riordan had been appointed as the Artistic Director of the Company and due to take up her post as of February 2014.
O'Riordan's 2006 stage version of Jonathan Safran Foer's Everything Is Illuminated was the Sunday Times critic's choice for four weeks running. Michael Billington wrote, in The Guardian, that it was "an intriguing story rather than a totally satisfying play. But it is one that is staged with deft economy by Rachel O'Riordan and well acted by the five-strong cast". while Dominic Cavendish writing for the Telegraph said "Having barely been able to wade through the book's overpoweringly pleased-with-itself prose, I found Simon Block's comparatively unfussy stage adaptation, directed by Rachel O'Riordan, a huge relief."
In 2011 O'Riordan took the role of artistic director at the Perth Theatre and Concert Hall where she has received critical acclaim. In her first season she was nominated at the Critics Awards Theatre Scotland awards for best director for Someone who'll watch over me by Frank McGuiness. The play was nominated in two other categories. In her career O'Riordan has received a number of various nominations including for Best Director in the TMA Awards for Much Ado About Nothing and The Absence of Women (both Lyric, Belfast), best director at the Irish Times Theatre Awards nomination for Sam Thompson's Over the Bridge.
Following its inclusion in the 2008 Edinburgh Fringe, Rachel won the Best Director award for the Owen O'Neill play Absolution in the First Irish Theatre Festival Awards in New York. Her 2013 production of The Seafarer was shortlisted in three categories at the annual Critics' Awards for Theatre in Scotland (CATS) for best ensemble, best production and best director. The production won 'Best ensemble' and saw O'Riordan pick up Best director award which critics announced 'cemented her position as one of the finest and most visionary directors in the country'.
- "Stage is set for change". Herald Scotland (04 April 2012). Herald & Times Group. Retrieved 26 November 2014.
- Richard Dormer speaking to Hannah Kennedy (29 March 2004). 20 Questions With...Richard Dormer. WhatsOnStage. Retrieved 26 November 2014.
- David Finkle (21 June 2004). Hurricane review. TheaterMania. Retrieved 26 November 2014.
- Allison Vale (2007).Animal Farm review. British Theatre Guide. Retrieved 26 November 2014.
- Tammy Moore (12 October 2010). "My Cultural Life: Rachel O'Riordan". Culture Northern Ireland. Retrieved 26 November 2014.
- Joe Nawaz (12 October 2012). THEATRE REVIEW: Write on the Edge. Culture Northern Ireland. Retrieved 26 November 2014.
- "Sherman Cymru Announces New Artistic Director". Sherman Cymru (15 October 2013). Retrieved 26 November 2014.
- Michael Billington (20 September 2006). "Everything is Illuminated", Hampstead, London. The Guardian. Retrieved 26 November 2014.
- Dominic Cavendish (21 September 2006). "Highlighting the Holocaust". The Telegraph. Retrieved 26 November 2014.
- "National Theatre of Scotland leads CATS nominations". The Stage, News (10 May 2012). Retrieved 26 November 2014.
- Laurence Mackin (15 January 2011). "The Irish Times Theatre Awards Shortlist December 2010". Irish Times. Retrieved 26 November 2014.
- "ABSOLUTION Comes To 59E59 Theatres 9/8-10/3". Off Broadway (05 August 2010). Retrieved 26 November 2014.
- Lyric puts local writer on national stage".Lyric Theatre. Retrieved 26 November 2014.
- Bill Dunlop (02 August 2008). "Absolution". Edinburgh Guide.com. Retrieved 26 November 2014.
- Owen O'neill. Retrieved 26 November 2014.
- "The Seafarer nominated for three awards". Lyric Theatre, News. Retrieved 26 November 2014.
- Alan Cumming and Blythe Duff win best actor awards. BBC News (09 June 2013). Retrieved 26 November 2014.
- Thom Dibin (09 June 2013). "Alan Cumming and Perth’s The Seafarer win at Scottish theatre awards". The Stage. Retrieved 26 November 2014.