Phoxocampus tetrophthalmus, the trunk-barred pipefish, is a species of marine fish belonging to the family Syngnathidae. This species can be found in reefs and tide pools of the Indo-Pacific specifically Indonesia, the Philippines, and Guam. They have also been observed in the Andaman, Cocos-Keeling, and Ryukyu islands. Their diet likely consists of small crustaceans Reproduction occurs through ovoviviparity in which the males brood eggs before giving live birth.