Abstract: Portable barbell apparatus is disclosed comprising a collapsible enclosure made of a synthetic polymeric material. The enclosure has a base and an aperture for filling the enclosure. The center of gravity of the enclosure is between the aperture and the base, an opening being provided in the enclosure for receiving the end of a weight supporting bar, the opening being positioned in between the center of gravity and the aperture. This arrangement allows for the positioning of a pair of the enclosures on either end of a weight supporting bar after which the enclosures may be filled with water, sand or other particulate material so that the assembly may be employed as a barbell. When not in use, the enclosures may be removed from the weight supporting bar, emptied and conveniently transported and/or stored. The aperture comprises a slit and has a resilient member extending around the periphery thereof to resiliently bias the slit to a closed position.