Abstract: A portable anti-theft device for attachment to a piece of portable outdoor furniture comprises a base attachable to the outdoor furniture and a hollow security shell attachable to the base. The base comprises a segmented tubular body comprising at least two semitubular segments and having an inner peripheral surface; longitudinally opposed stops extending outwardly from the base, and a closure for attaching, the base to the portable outdoor furniture. The hollow security shell comprises a first shell segment and a second shell segment (the first and second shell segments defining an enclosed internal space with a pair of vertically-opposed apertures), and a hinge joining said first and second half shells, the security shell being configured to enclose the closure.