Borchgrevinkium is an extinct genus of chelicerate arthropod. A fossil of the single and type species, B. taimyrensis, has been discovered in deposits of the Early Devonian period (Lochkovian epoch) in the Krasnoyarsk Krai, Siberia, Russia. The name of the genus honors Carsten Borchgrevink, an Anglo-Norwegian explorer who participated in many expeditions to Antarctica. Borchgrevinkium represents a poorly known genus whose affinities are uncertain.

It had several unique characteristics that differentiated it from many other arthropods, such as its long parabolic (nearly U-shaped) prosoma (head), its elongated first and second segments and the presence of paired "ridges" in the surface of its third to tenth tergites (dorsal halves of the segments). Furthermore, the opisthosoma (the "trunk") of Borchgrevinkium was triangular, and its telson (the posteriormost division of its body), short and wedge-shaped. It was a small animal, approximately 3 centimetres (1.2 inches) long.

The only known specimen of the genus was collected in 1956 and described in 1959 by the Russian paleontologist Nestor Ivanovich Novojilov. He determined that it was a eurypterid and classified it in the family Mycteroptidae. However, its classification changed repeatedly over the years, being transferred from Eurypterida to Xiphosura and back to Eurypterida some time later. Borchgrevinkium is tentatively considered as a prosomapod, with more fossil material needed to ensure its current classification.

The size of the only known specimen of Borchgrevinkium, identified with the label PIN 1271/1, is estimated more or less at 3 centimetres (1.2 inches), making it a small arthropod.

The prosoma was longer than wider (covering one third of the length of the animal), parabolic (nearly U-shaped) and with a length of 1.35 cm (0.53 in). The eyes are not preserved and therefore, their position or shape is unknown. The prosomal appendages (limbs) are only known by the tip of poorly preserved left pairs. They were short, undifferentiated and spiniferous. The opisthosoma (the "trunk") was triangular and 1.23 cm (0.48 in) long. It was composed of 12 segments, with the first one being exceptionally long and forming with the second segment an "extension" of the prosoma. The genital appendage (a ventral "rod" part of the reproductive system) of Borchgrevinkium was long, spanning from its first to its second segment.

The third to tenth tergites (dorsal halves of the segments) had distal (outwards-pointing) lobes on their sides that delimitated the dorsal and ventral parts of the opisthosoma. Furthermore, these tergites had on their surfaces converging paired "folds" or "ridges" that progressively narrowed to the center of the tenth tergite. These ridges were almost parallel to the lateral lobes. On the eleventh tergite, the edges were slightly curved. The pretelson (the segment that preceded the telson) had a bifid (divided into two lobes) dorsal projection. The telson (the posteriormost division of the body) was cuneiform (wedge-like), short and narrow, and measured 0.45 cm (0.18 in). The ornamentation of the body was composed by short scales with broadly rounded edges.

In 1956, the Russian paleontologist and geologist Vladimir Vasilyevich Menner discovered a series of fossils in Devonian deposits near the Imangda River at the southwest of the Taymyr Peninsula, near Norilsk, in the Krasnoyarsk Krai (Russia, then the Soviet Union). He sent them to the Russian paleontologist Nestor Ivanovich Novojilov, who in 1959 described, among others, a specimen labelled as PIN 1271/1, which was nearly complete. It was deposited in the Paleontological Institute of the Russian Academy of Sciences, in Moscow, where it remains. Novojilov considered it unique enough to be erected as a new genus, Borchgrevinkium, named after the Anglo-Norwegian explorer Carsten Borchgrevink for his expeditions to Antarctica. He compared it with the then xiphosuran genus Weinbergina, assuming that Borchgrevinkium was also a xiphosuran. However, the Norwegian paleontologist Leif Størmer, who assisted him during his study, noticed that what Novojilov had considered to be an accidental fissure was actually part of the "macrosegment" (the first segment), finding as well the tip of the appendages after closer examination. The presence of this macrosegment convinced Novojilov that Borchgrevinkium represented a new eurypterid, and he classified it as such.

In 1966, the American paleontologist Erik Norman Kjellesvig-Waering, during a study on the families and genera of the superfamily Stylonuracea (now known as Stylonuroidea), tentatively recorded an Upper Silurian occurrence of the genus Borchgrevinkium apart from the Lower Devonian one, believing that a new specimen had been found. This specimen was later named as "Borchgrevinkium sp.". In 2017, the British geologist and paleobiologist James C. Lamsdell and the Irish palaeontologist Derek Briggs found that this specimen was YPM IP 300790, collected in the Bertie Formation in the state of New York in 1967 by Samuel J. Ciurca, Jr., who identified it as a new undescribed species of Borchgrevinkium after contacting Størmer. Nevertheless, since this specimen was misidentified, it was redescribed as a new species of the chasmataspidid Diploaspis, D. praecursor, by Lamsdell and Briggs.