Described is a dispenser for dispensing a fluid, made of plastic material, including: —a ring nut having an inner cylindrical wall equipped with partial grooves; —a concertina-like deformable element, defining a return spring of the dispenser and including a cylindrical lower projection equipped with relative partial grooves; —a ring designed to define with the ring nut a locking system designed to define an operating configuration and a non-operating configuration of the dispenser in such a way as to pull the concertina-like deformable element in such a way as to align the partial grooves of the cylindrical wall of the ring nut and the partial grooves of the concertina-like deformable element.