Gillian Sanders was born on 15 October 1981 in Pietermaritzburg and took up triathlon in her youth under the influence of her father and older sister, who both competed in the sport.
Gillian was a member of the South African Mixed relay team- with Henri Schoeman, Kate Roberts and Richard Murray that took second place in the event at the 2014 Commonwealth Games held in Glasgow. All four athletes on a team must complete a super-sprint triathlon - 300m swim, approx 6.6km bike and 1km run - before tagging off to a teammate.
After competing internationally in age group and junior competition Sanders put her triathlon career on hold whilst studying law at Stellenbosch University, where she competed as a 1500m runner. She resumed triathlon competition after graduating, combining it with legal work.
Sanders chose to focus on full-time competition at the end of 2011. She competed in the Women's event at the 2012 Summer Olympics.