A platform for a fan of a turbomachine that will be mounted on a hub of the fan between two adjacent blades, the platform comprising a principal wall with a longitudinal principal orientation, that has a curved shape along the longitudinal direction, and a stiffener that is mounted on a lower face of the principal wall, of which the section of the stiffener, in a plane perpendicular to the longitudinal direction is globally in the form of a U open towards the principal wall. The stiffener comprises at least two straight segments inclined relative to each other and inclined relative to the longitudinal principal direction.