Our Team

Mark O'Shaughnessy
Share This

Mark is a litigation and regulatory investigations partner in ByrneWallace LLP.

Mark advises domestic and international organisations on complex disputes with a particular focus on corporate disputes, contentious intellectual property and insurance matters in the education, health, life science and TMT sectors.

He also has extensive experience in advising private, semi-state and public organisations in the context of regulatory investigations and enquiries. 

Reputation management is core to Mark's expertise and he has managed the corporate reputation strategies of numerous companies through times of crisis.

Mark has also been appointed by the European Commission as a member of its Expert Group against SLAPP (Strategic Lawsuits Against Public Participation).

Key Experience

  • Managing strategic corporate disputes for publically listed companies, multinational corporations and large Irish companies.
  • Advising businesses on contractual disputes, minority oppression actions and quasi-partnership disputes before the Commercial Court and High Court.
  • Acting for organisations in intellectual property disputes, particularly patent disputes and passing-off actions.
  • Advising on insurance policy interpretation and coverage with a particular focus on business interruption insurance, D&O insurance and environmental impairment liability insurance.
  • Advising organisations during internal investigations and managing external engagements with regulatory bodies and parliamentary committees. 
  • Advising domestic and international companies on protecting their corporate reputations both online and in traditional media.


  • Law and Accounting, University of Limerick, 2003
  • Admitted as a Solicitor, Law Society of Ireland, 2008
  • Diploma in Commercial Litigation, Law Society of Ireland, 2009
  • Professional Diploma in Arbitration, University College Dublin, 2011


  • Law Society of Ireland
  • Law Society of England and Wales
  • Dublin Solicitors Bar Association
  • Arbitration Ireland
  • British Irish Commercial Bar Association


‘Mark O’Shaughnessy is smart, emotionally committed and very inspiring.’ – Legal 500, 2021

‘I found Mark O’Shaughnessy to be excellent in all respects. I felt he was exceedingly engaged and energised by the matter and was wholly committed to our interests. I found this level of commitment to be quite different from other legal engagements where the client is sometimes made to feel to be nuisance in a busy day of other, more important matters.’ – Legal 500, 2021

‘We are involved in a number of cases to protect the business and to manage reputational risk. These are being litigated in the High Court currently. We are using the services of Mark O’Shaughnessy, who has an excellent legal mind and who is highly responsive to client needs in the area of defamation. This is a new area of litigation for the business and Mark is very strong at ensuring complex legal matters are explained in clear and concise language so that the business can make informed decisions in terms of strategy and tactics.’

‘I have also worked with Mark O’Shaughnessy who is top-class in the area of copyright law.’ – Legal 500, 2021

‘Referred to the Intellectual team we were delighted to meet Mark O’Shaughnessy and his team and were comforted by their grasping of the matter, their ability to communicate complex legal concepts and their ability to clearly strategise the most efficient path to manage the threat. I would commend their capacity to communicate the complex in a clear and productive style.’ – Legal 500, 2021