The invention concerns a preform for a container made of plastic material, comprising a cylindrical body that extends along an axis of revolution of the preform and a bottom that closes the cylindrical body. The bottom has an outer profile with a central portion and a curved portion joining the central portion to the cylindrical body. The central portion has, in longitudinal cross-section, a first concave section. The curved portion has successively, in longitudinal cross-section, from the first concave section towards the cylindrical body, a first convex or frustoconical section, a second concave section and a second convex or frustoconical section.