An undercarriage liner made of plastic for a vehicle is detachably attached to the adjacent vehicle chassis. In order for an undercarriage liner to have a significantly lower weight per unit of area, and thus a definitely reduced total weight, while retaining the same flexural strength and impact strength, the undercarriage liner, in the form of a sandwich structure, has a lightweight core layer of polypropylene foam or unconsolidated glass-mat-reinforced thermoplastic. The core layer is provided with a thin cover layer of polypropylene fiber-reinforced polypropylene on both sides. The two rigid and high-impact cover layers are each thermally bonded to the core layer.