Pachycereus marginatus is a species of plant in the Cactaceae family. (Also sometimes called "Mexican Fencepost Cactus".) It has columnar trunks that grow slowly to 12 feet (3.7m) and may reach 20 feet (6.1m) in height. Stems are 3 to 4 inches (9–10 cm) in diameter; ribs 5 to 7 inches (13–18 cm). Its central spine is about 3/8 inch (1 cm) in diameter with 5-9 radials and slightly yellowish in colour. Its cuttings are sometimes used to create a fences as it its spines are not a large or dangerous as some cacti.