Oyat avocats Paris - Marie-Hélène Tonnellier

Marie-Hélène Tonnelier

Founding Partner · Digital/IP

Oyat avocats Paris - Marie-Hélène Tonnellier

Member of the Paris Bar since 1990, Marie-Hélène co-founded Oyat in 2022.

Marie-Hélène began her career in London within a solicitors’ firm prior to joining Moquet Borde & Associés (Paul Hastings) in 1990, then Jeantet in 1995. Then she has been a partner for 22 years at Latournerie Wolfrom Avocats where she created the digital and intellectual property department.

Marie-Hélène is one of the leading lawyers in the digital world. She advises and litigates on all issues related to IT projects, innovations (AI, robots, etc.), e-commerce and personal data. She also intervenes in media law and intellectual property.

Highly skilled in the sectors of distribution, tourism, luxury, new economy, mobility, media or services, she assists her clients in the implementation of strategic projects or in their digital transformation, helps them navigate through the various new rules in these various fields, assists them in often complex and innovative litigations.

Her oyat is between the Garde Guérin and petite Salinette beach: her breton paradise!


  • University of Panthéon-Sorbonne Paris I – Post graduate degree (DEA) in Business Law
  • University of Panthéon-Assas Paris II – Post graduate degree (DESS) of Notary Law
  • University of Panthéon-Sorbonne Paris I – Master’s Degree Droit des affaires


French, English


  • Lecturer at the University Paris XI-Saclay, Master Intellectual Property and Digital Law
  • Lecturer at the HEAD school, Master Digital and Intellectual Property Law
  • Former President of the IFCLA
  • Member of the Board of Directors of AFDIT
  • Member of the International Bar Association (IBA)



Best Lawyers 2024

  • Advertising Law
  • Information Technology Law
  • Intellectual Property Law


Best Lawyers 2024 & 2023

“Lawyer of the Year”


Legal 500 EMEA 2023 

  • Marie-Hélène Tonnellier / Leading individual
  • IT and Internet
  • Telecoms / Firm to watch

Marie-Hélène Tonnellier understands quickly her client’s needs and transforms them into results; an excellent negotiator who adapts swiftly to unforeseen situations.’

‘Marie-Hélène Tonnellier is the Queen of TMT in France and is always my go-to resource for French legal advice in this sector, whether technology contracting, intellectual property or data privacy matters.’


Décideurs Juridiques / Leaders League 2023

/ Innovation, Technology & Telecoms

  • Data protection law / Excellent
  • IT, software & digital projects / Excellent
  • Internet / Excellent

/ Medias & Entertainment

  • Online gaming and betting / Excellent


Palmarès of “les meilleurs cabinet d’avocats en France 2023” by le Point

  • Literary and artistic property law / 5 stars
  • New Technologies, IT and Communication Law / 5 stars


Chambers 2023

  • TMT Information Technology

Who’s Who Legal 2022-2023

  • Data – Data Privacy & Protection 2023, Data Information Technology 2023 / Global Leader
  • Data – Information Technology 2023 / Global Leader
  • France – Data 2023 / National Leader