Ekiden de l'Estuaire is a relay marathon held in Saint-Nazaire, located on France's Loire-Atlantique coast within the Pays de la Loire region. This road race covers the full marathon distance of 42.195 km, with teams dividing the distance in the ekiden style rather than a single runner completing the entire course. Scheduled for early April, the race takes place in a public park setting within the city, differing from remote trail or point-to-point countryside routes.
The course consists of a single 42.195 km loop, meaning the event centers around one marathon circuit through Saint-Nazaire. This format is suitable for groups of friends, club members, and mixed-ability teams, as the primary challenge involves collective pacing and efficient relay exchanges. The event organizers also highlight nearby Nantes, La Baule, and Guerande, positioning the race as part of a weekend experience on the estuary, with proximity to beaches, city areas, and towns in Loire-Atlantique.