A collapsible cargo container is disclosed wherein end walls are pivoted into the container when empty and locked against the roof, and then side walls buckle via hinges into a folded configuration. The folded configuration is achieved easily with a modified spreader without the need to otherwise disassemble or deconstruct the container, leaving no loose parts or tools. The cargo container preferably constructed with an improved light weight panel that facilitates loading of the container while improving strength and reducing weight.