A new guitarfish of the genus Pseudobatos is described based on 82 specimens obtained from the Gulf of California. Sixty-three morphometric measurements were taken on all specimens, and on ten specimens from each of three congeners. A principal component analysis and linear discriminant analysis were performed on these morphometric data for discrimination. The new species (∼685 mm TL) is most similar to Pseudobatos productus but differs in having a narrower maximum disc width (30–35% vs. 36–38% TL), shorter distance from nostril to disc margin (2.8–4.0% vs. 4.2–5.2% TL), narrower disc width at anterior orbit (12–19% vs. 20–22% TL), and a narrower tip of snout width (3% vs. 4–6% TL). The species is also less densely scaled between the orbits and has less pronounced rostral thorns than Pseudobatos productus. A key to the guitarfishes of the Gulf of California is also provided.