Lusotitan (phonetically spelled as Lu-so-tie-tan) also known as Lusitania titan is a Atalaiensis type species named by Octavio Mateus and Migues Telles Antunes in 2003. It also has the synonym of Brachiosaurus atalaiensis. The classification of this species is as follows: Chordata – Reptilia – Dinosauria – Saurischia – Sauropodomorpha – Sauropoda – Brachiosauridae

Lusotitan are estimated to be about 25 meters long and follow a herbivorous diet. The known location of this species includes the Lourinhã Formation in the Portugal. They existed during the Tithonian period of the Jurassic. The fossilized representation of this species includes the partial post cranial remains mainly of vertebrae and some elements of the limb bones. No skull has been found so far.

Lusotitan is a genus of herbivorous brachiosaurid sauropod dinosaur from the Late Jurassic Period of Portugal. Manuel de Matos, who was a member of the Geological survey of Portugal discovered large sauropod fossils in the Portuguese Lourinhã Formation in 1947. These fossils date back to the Tithonian stage of the Late Jurassic period. The finds consisted of a partial skeleton lacking the skull and individual vertebrae uncovered in several locations. They were named as a new species of Brachiosaurus by Albert-Félix de Lapparent and Georges Zbyszewski in 1957. The specific name refers to the site Atalia. The generic name is derived from Luso, the Latin name for an inhabitant of Lusitania, and from the Greek word "Titan", a mythological giant. Octávio Mateus and Miguel Telles Antunes renamed them as a separate genus Lustonian. One of the reasons Mateus assigned it to the Brachiosauridae was that it had long forearms

Lapparent did not assign a holotype to the fossils. Mateus chose the skeleton as the lectotype in 2003. Its bones have the inventory numbers MIGM 4798, 4801-10, 4938, 4944, 4950, 4952, 4958, 4964-6, 4981-2, 4985, 8807, and 8793-5. These remains include 28 vertebrae and elements of the appendicular skeleton.

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