- R.J. O'BRIEN LIMITED- 01810354 - Incorporated on 19 April 1984 
- DR. SINEAD O'BRIENActive - Proposal to Strike off- NI605325 - Incorporated on 30 November 2010 
- DR. CELINE O'BRIENActive - Proposal to Strike off- NI606251 - Incorporated on 21 February 2011 
- DR LAOISE O'BRIEN- NI625708 - Incorporated on 16 July 2014 
- M L O'BRIEN LIMITED- 09023869 - Incorporated on 6 May 2014 
- E A O'BRIEN LIMITEDDisolved- 11911895 - Dissolved on 22 August 2023 
- SHAUN O'BRIEN LTDDisolved- 14470733 - Dissolved on 16 April 2024 
- TRIM O’BRIENS LTDDisolved- 13243415 - Dissolved on 21 June 2022 
- MARY O'BRIENS LTD- 14972580 - Incorporated on 30 June 2023 
- O'BRIEN T LIMITED- 15023721 - Incorporated on 24 July 2023 
- S O'BRIEN BUILD LTD- 15177972 - Incorporated on 30 September 2023 
- J & E A O'BRIEN LIMITEDActive - Proposal to Strike off- 07461685 - Incorporated on 7 December 2010 
- G. F. O'BRIEN LIMITEDDisolved- 01413564 - Dissolved on 4 January 2022 
- T. & R. O'BRIEN LIMITED- SC043750 - Incorporated on 26 July 1966 
- W G M O'BRIEN LIMITEDActive - Proposal to Strike off- 03455893 - Incorporated on 27 October 1997 
- ANNIS & O'BRIEN LTD- 09633605 - Incorporated on 11 June 2015 
- J O'BRIEN 7 LIMITEDLiquidation- 08301638 - Incorporated on 21 November 2012 
- NIALL O'BRIEN LTDActive - Proposal to Strike off- 09567046 - Incorporated on 29 April 2015 
- GAVIN O'BRIEN LTD- 10706436 - Incorporated on 4 April 2017 
- KITTY O'BRIEN LTD- 13737740 - Incorporated on 11 November 2021