Altispinax (/ˌæltɪˈspaɪnæks/; "with high spines") is a genus of large predatory theropod dinosaur from the Early Cretaceous period (Valanginian, 140 to 133 million years ago) of what is now the Wadhurst Clay Formation of East Sussex, England.

Probably during the early 1850s, fossil collector Samuel Husbands Beckles discovered some nodules with dinosaur bones in a quarry near Battle, East Sussex.

Owen, who referred the specimens to Megalosaurus bucklandii, thought the vertebrae were part of the shoulder region and it has been assumed that he must have already known of the find in 1853 as he directed Benjamin Waterhouse Hawkins to put a hump on the back of his life-sized Megalosaurus sculpture in Crystal Palace Park, which again inspired other restorations from the 19th century.

[3][4] The fossil, now catalogued as NHMUK R1828, was probably found in a layer of the Hastings Bed Group dating from the late Valanginian age.

[5] In 1888, Richard Lydekker compared these vertebrae with material referred to Megalosaurus dunkeri, a Cretaceous species represented by a single tooth found in Germany.

He used the three vertebrae as the basis for this genus, noting that they were different from Megalosaurus, and created the name Altispinax (meaning "with high spines") based on their appearance.

Paul in 1988 tentatively estimated that Altispinax weighed 1 tonne (1.1 short tons) and was shorter than the type specimen of Acrocanthosaurus atokensis which measures about 8 meters (26 ft) long.

[8] The three A. dunkeri back vertebrae from Sussex have about thirty-five centimetres high neural spines or processus spinosi, about as relatively tall as those of Ichthyovenator.

Naish also pointed out that Owen had noted the large depressions on the neural arch sides and had explained them as a result of pneumatisation, the first time this phenomenon would explicitly have been observed with a dinosaur.

[19] The discovery of a back crest incorporating only two high vertebrae in Concavenator, in 2010 provided corroboration that the short anterior Altispinax spine may be complete.