三棱龙属（学名：Trilophosaurus）是种已灭绝双孔亚纲爬行动物，生存于三叠纪晚期，外表类似蜥蜴，跟主龙类有接近亲缘关系。三棱龙是种草食性动物，身长可达2.5公尺。头骨短而厚重，有宽广平坦的颊齿，表面锐利，可切断坚硬的植物。前上颌骨与下颌前部缺乏牙齿，牠们生前可能有角质覆盖的喙状嘴。

三棱龙的头骨也很独特，因为牠们的下颞孔消失了，使牠们看起来像是阔孔类爬行动物的头骨，所以三棱龙类最初跟楯齿龙目、鳍龙超目一起被归类于阔孔亚纲。在1988年，Robert L. Carroll提出下颞孔消失是为了使头骨强化。

Trilophosaurus (Greek for "Lizard with three ridges") is a lizard-like trilophosaurid allokotosaur known from the Late Triassic of North America. It was a herbivore up to 2.5 m long. It had a short, unusually heavily built skull, equipped with massive, broad flattened cheek teeth with sharp shearing surfaces for cutting up tough plant material. Teeth are absent from the premaxilla and front of the lower jaw, which in life were probably equipped with a horny beak.