The straight-tusked elephant (Palaeoloxodon antiquus) is an extinct species of elephant that inhabited Europe and Western Asia during the Middle and Late Pleistocene. One of the largest known elephant species, mature fully grown bulls on average had a shoulder height of 4 metres (13 ft) and a weight of 13 tonnes (29,000 lb), placing them among the largest land mammals ever. Straight-tusked elephants likely lived very similarly to modern elephants, with herds of adult females and juveniles and solitary adult males. The species was primarily associated with temperate and Mediterranean woodland and forest habitats, flourishing during interglacial periods, when its range would extend across Europe as far north as Great Britain and Denmark and eastwards into Russia, while persisting in southern Europe during glacial periods, when northern Europe was occupied by steppe mammoths and later woolly mammoths. Skeletons found in association with stone tools and in one case, a wooden spear, suggest they were scavenged and hunted by early humans, including Homo heidelbergensis and their Neanderthal successors.

The species is part of the genus Palaeoloxodon (whose other members are also sometimes called straight-tusked elephants), which emerged in Africa during the Early Pleistocene, before dispersing across Eurasia at the beginning of the Middle Pleistocene, with the earliest record of Palaeoloxodon in Europe dated to around 800–700,000 years ago, around the time of the extinction of the previously dominant mammoth species Mammuthus meridionalis. The straight-tusked elephant is the ancestor of over half a dozen named (and several more unnamed) species of dwarf elephants that inhabited islands in the Mediterranean, some of which shrunk to only 2% the size of their mainland ancestor. The straight-tusked elephant became extinct during the latter half of the Last Glacial Period, with the youngest remains found in the Iberian Peninsula, dating to around 44,000 years ago. Possible even younger records include a single tooth from the Netherlands that has been dated to around 37,000 years ago, and footprints from the southern part of the Iberian Peninsula dated to 28,000 years ago.

The body, including the pelvis, of P. antiquus was broad relative to extant elephants. The forelimbs, particularly the humerus, and the scapula are proportionally longer than those of living elephants, resulting in a high position of the shoulder. The head represents the highest point of the animal, with the back being somewhat sloped though irregular in shape. The spines of the back vertebrae are noticeably elongate. The tail was relatively long. Although not preserved, the body was probably only sparsely covered in hair, similar to extant elephants, and probably had relatively large ears.

The skull is proportionally both very wide and tall. Like many other members of the genus Palaeoloxodon, P. antiquus possesses a well-developed growth of bone at the top of the cranium above the nasal opening called the parieto-occipital crest, originating from the occipital bone of the skull roof which projects forwards and overhangs the rest of the skull. The crest was probably an anchor for muscles, including the splenius, as well as an additional muscle layer that wrapped around the top of the head, called the "extra splenius". The latter was likely similar to the "splenius superficialis" found in Asian elephants. The crest likely developed to support the very large size of the head, as the skulls of Palaeoloxodon are the largest proportionally and in absolute size among proboscideans. Two morphs of P. antiquus were previously thought to exist in Europe on the basis of differences in the parieto-occipital crest, one more similar to the South Asian Palaeoloxodon namadicus. These differences were shown to be age-related (ontogenetic variation), with the crest being more pronounced in older individuals, as well as due to distortion during fossilisation (taphonomic variation). P. antiquus differs from P. namadicus in having a less stout cranium and more robust limb bones, and in lacking a teardrop-shaped indentation behind the eye socket (infraorbital depression). The premaxillary bones (which contain the tusks) are fan-shaped and very broad in front view. The tusks are very long relative to the size of the body and vary from straight to slightly curved. The teeth are high crowned (hypsodont), with each third molar having approximately 16–21 lamellae (ridges).

The species was sexually dimorphic, with males being substantially larger than females; this size dimorphism was more pronounced than in living elephants. P. antiquus was on average considerably larger than any living elephant, and among the largest known land mammals to have ever lived. Under optimal conditions where individuals were capable of reaching full growth potential, 90% of mature fully grown straight-tusked elephant bulls are estimated to have had shoulder heights in the region of 3.8–4.2 m (12.5–13.8 ft) and a weight between 10.8–15 tonnes (24,000–33,000 lb). For comparison, 90% of mature fully grown bulls of the largest living elephant species, the African bush elephant under optimal growth conditions have heights between 3.04 to 3.36 metres (10.0 to 11.0 ft) and masses between 5.2–6.9 tonnes (11,000–15,000 lb). Extremely large bulls, such as those represented by a now lost pelvis and tibia collected from the Iberian Peninsula (including the San Isidro del Campo site in Spain) in the 19th century, may have reached shoulder heights of 4.6 m (15.1 ft) and body masses of over 19 tonnes (42,000 lb), exceeding the body mass estimated for the largest specimens of Paraceratherium transouralicum, the otherwise largest known land mammal. Adult males had tusks typically around 3.5–4 metres (11–13 ft) long, with masses comfortably exceeding 100 kilograms (220 lb). The preserved portion of one particularly large and thick tusk from Aniene, Italy, is 3.9 metres (13 ft) in length, has a circumference of around 77 centimetres (30 in) where it would have exited the skull, and is estimated to have weighed over 190 kilograms (420 lb) in life.

Females were considerably larger than living female elephants and comparable in size with African bush elephant bulls, with female individuals from the Neumark Nord population in Germany reaching shoulder heights and weights rarely exceeding 3 metres (9.8 ft) and 5.5 tonnes (12,000 lb) respectively (though several relatively young females at the site would likely have exceeded this size when fully grown). A particularly large female known from a pelvis found near Binsfeld in Germany has been estimated to have had a shoulder height of 3.3 metres (10.8 ft) and a weight of 7.5 tonnes (17,000 lb). For comparison, 90% of fully grown female African bush elephants reach an shoulder height of 2.47 to 2.75 metres (8.1 to 9.0 ft) and body mass of 2.6 to 3.5 tonnes (5,700 to 7,700 lb) under optimal growth conditions. Newborn and young calves were likely around the same size as those of modern elephants. A largely complete 5 year old calf from Cova del Rinoceront in Spain was estimated to have a shoulder height of 178–187 centimetres (5.8–6.1 ft) and a body mass of 1.45–1.5 tonnes (3,200–3,300 lb), which is comparable to a similarly aged African bush elephant.

In the second century AD, the Greek geographer Pausanias remarked that the Megalopolis region in the central part of the Peloponnese peninsula in southern Greece was known for its enormous bones, which Pausanias reported were considered to be those of giants who died during the Gigantomachy, a mythic climactic battle between the giants and the Greek gods. Given that this region is today known for its straight-tusked elephant fossils, it is plausible that at least some of the giant bones to which Pausanias referred were those of straight-tusked elephants.

In 1695, remains of a straight-tusked elephant were collected from travertine deposits near Burgtonna in what is now Thuringia, Germany. While these remains were originally declared to be purely mineral in nature by the Collegium Medicum in the nearby city of Gotha, Wilhelm Ernst Tentzel, a polymath in the employ of the ducal court of Saxe-Gotha-Altenburg, correctly identified them as elephant remains. The Burgtonna skeleton was one of the specimens that Johann Friedrich Blumenbach described in his publication naming the woolly mammoth (Mammuthus primigenius, originally Elephas primigenius) in 1799. The remains of straight-tusked elephants continued to be attributed to woolly mammoths until the 1840s.⁴⁰