Mars bleu - Auch is the Souffle du Gers, a running event held in Auch, Gers, southwest France. The main race is a 21.1 km half marathon, beginning in the morning on Avenue du Général-de-Gaulle. The event supports Mars Bleu, the French awareness campaign against colorectal cancer.
The route passes through Auch and nearby communes, including Pavie, Auterrive, Boucagnères, Orbessan, and Sansan. Athlétic Club Auscitain organizes the event with the departmental committee and local councils. Numerous volunteers assist on the day, giving the race a distinct local, community-supported character.