Martyn Day is a British solicitor specializing in international, environmental and product liability claims who founded — and is the Senior Partner of — the law firm Leigh Day.
He was a director of Greenpeace Environmental Trust, having stepped down as chairman of Greenpeace UK in 2008.
Examples of his work include negotiating settlements for approximately 1,300 Kenyans injured/killed by British Army munitions, for 52 Colombian farmers in a claim against BP relating to the damage caused to farms in the north of the country for residents of Abidjan after the disposal of waste in the Ivory Coast has led to deaths and injuries in Abidjan and Iraqis alleging torture by British soldiers.
He is the co-author of Toxic Torts, Personal Injury Handbook, Multi-Party Actions and Environmental Action: A Citizens Guide.
In April 2008 Day was identified by The Times as one of the UK's most powerful and influential lawyers.
In late 2014 Leigh Day was referred to the Solicitors Regulation Authority for issues arising from the Al-Sweady Inquiry.