The aim of this case study is to describe the nutrition practices of a female recreational runner (VO₂max 48.9 ml·kg^-1·min^-1) who completed 26 marathons (42.195 km) in 26 consecutive days. Information relating to the nutritional intake of female runners during multi-day endurance events is extremely limited, yet the number of people participating year-on-year continues to increase. This case study reports the nutrition intervention, dietary intake, body composition changes and performance in the lead-up and during the 26 days. Prior to undertaking the 26 marathon challenge, three consultations were held between the athlete and a sports nutrition advisor; planning and tailoring the general diet and race-specific strategies to the endurance challenge. During the marathons, the mean energy and fluid intake was 1039.7 ± 207.9 kcal (607.1 – 1453.2) and 2.39 ± 0.35 L (1.98 – 3.19). Mean hourly carbohydrate intake was 38.9 g·hr^-1. 11 days following the completion of the 26 marathons, body mass had reduced by 4.6 kg and lean body mass increasing by 0.53 kg when compared with 20 days prior. This case study highlights the importance of providing general and event-specific nutrition education when training for such an event. This is particularly prudent for multi-day endurance running events.

• Multi-day endurance running (MDER) events are increasingly prevalent among recreational and elite runners, as such, reporting the practices of populations underrepresented in the literature are important.

• This case study reports nutritional practices of a female recreational runner undertaking 26 marathons in 26 consecutive days.

• This case study highlights the importance of providing general and event-specific nutrition education when training for such an event. This is particularly prudent for MDER events.