Haestasaurus is a genus of herbivorous sauropod dinosaur, belonging to the Macronaria, that during the Early Cretaceous lived in the area of present-day England.

The upper surface of the radius has, measured from front to rear, its largest width along the outer rim, which edge is nearly straight instead of strongly convex.

In 1852, the collector Samuel Husband Beckles obtained a block of Wealden Sandstone that had become visible at low tide off the coast of East Sussex near Hastings.

[4] Pelorosaurus becklesii at first received little attention, perhaps also because the fossils remained in the private collection of Beckles; they were acquired by the British Museum (Natural History) in 1891.

In 1888, Richard Lydekker described a cast present in the museum, BMNH R28701, but seemed to be unaware of its status as a separate species and misidentified the discovery site as the Isle of Wight.

[7][8][9] In 1932, Friedrich von Huene concluded that P. becklesii represented a separate genus but provided no name, referring to it as "Gen.

[11] In 2015, Paul Upchurch, Philip D. Mannion and Michael P. Taylor, having established that P. becklesii differed in many traits from Pelorosaurus conybeari and was not its sister species, named the separate genus Haestasaurus.

When the Beckles Collection was acquired, a metacarpal was referred to P. becklesii, specimen NHMUK R1869, but its large size precludes its belonging to the holotype.

The 2015 study performed some detailed cladistic analyses to establish the exact position of Haestasaurus in the evolutionary tree.

Alternatively, Haestasaurus was a basal member of the larger clade of the Macronaria, a close relative of Camarasaurus, Janenschia or Tehuelchesaurus.