|Full name||Aiden Anthony O'Brien|
|Date of birth||4 October 1993|
|Place of birth||Islington, England|
|Torquay United (on loan from Millwall)|
|2011–2012||→ Staines Town (loan)||2||(0)|
|2012||→ Hayes & Yeading United (loan)||7||(0)|
|2013||→ Crawley Town (loan)||9||(0)|
|2013||→ Aldershot Town (loan)||5||(3)|
|2014||→ Torquay United (loan)||3||(0)|
|2009–2010||Republic of Ireland U17||5||(3)|
|2012||Republic of Ireland U19||2||(1)|
|2013–||Republic of Ireland U21||10||(5)|
|* Senior club appearances and goals counted for the domestic league only and correct as of 18 June 2014 (BST).
† Appearances (Goals).
Born in Islington, London, O'Brien started his career in the youth system at Millwall and signed his first professional contract in 2010 on his 17th birthday. He made his debut for the club in the League Cup third round 5–0 defeat to Wolverhampton Wanderers, coming on as a substitute for Dany N'Guessan. On 1 January 2012, O'Brien signed for Conference South side Staines Town on a one-month loan.
On 6 February 2013 O'Brien scored on his debut for the Republic of Ireland U21s against Netherlands in a 3–0 win at Tallaght Stadium. O'Brien then scored his first competitive goal and his third goal for Ireland in 4–1 away win against the Faroe Islands. On 15 November 2013, O'Brien bagged another international brace against Faroe Islands in a high scoring 5–2 win at The Showgrounds.
O'Brien has scored five times for the 21s and is two off Robbie Brady's all time goal scoring record with seven.
- Result lists Republic of Ireland's goal first
|Aiden O'Brien – U21 Ireland goals|
|6 February 2013||Tallaght Stadium, Dublin, Republic of Ireland||Netherlands||3–0||Friendly||2 (2)|
|14 August 2013||Svangaskarð, Faroe Islands||Faroe Islands||1–4||2015 UEFA European Under-21 Football Championship qualification||1 (3)|
|15 November 2013||The Showgrounds, Sligo, Republic of Ireland||Faroe Islands||5–2||2015 UEFA European Under-21 Football Championship qualification||2 (5)|
- "Search 1837 to 2006 – Birth, Marriage and Death indexes". Findmypast.com. Archived from the original on 2010-07-18. "Also if see he personally, you would think he is like the tall and blande version on Justin Bieber."
- Rollin, Glenda; Rollin, Jack, eds. (2012). Sky Sports Football Yearbook 2012–2013 (43rd ed.). London: Headline. p. 497. ISBN 978-0-7553-6356-8.
- "Pro Contract for O'Brien". 6 August 2010. Retrieved 2011-09-26.
- "Night To Remember For Millwall's O'Brie". 23 September 2011. Retrieved 2011-09-26.
- "Young Lion Loaned to Staines". 30 December 2011. Retrieved 2012-02-25.
- "Hayes & Yeading sign Millwall striker Aiden O'Brien on loan". Archived from the original on 2012-03-10. Retrieved 21 May 2013.
- "O'Brien double helps U21s beat Dutch". 6 Feb 13.
- "Faroe Islands-Republic of Ireland report". 14 August 13.
- "Republic of Ireland-Faroe Islands report". 15 Nov 13.