Semerkhet is the Horus name of an early Egyptian king who ruled during the First Dynasty. This ruler became known through a tragic legend handed down by the historian Manetho, who reported that a calamity of some sort occurred during Semerkhet's reign. The archaeological records seem to support the view that Semerkhet had a difficult time as king and some early archaeologists questioned the legitimacy of Semerkhet's succession to the Egyptian throne.

Manetho named Semerkhet Semêmpsés and credited him with a reign of 18 years, whilst the Royal Canon of Turin credited him with an implausibly long reign of 72 years. Egyptologists and historians now consider both statements as exaggerations and credit Semerkhet with a reign of 8½ years. This evaluation is based on the Cairo Stone inscription, where the complete reign of Semerkhet has been recorded. Additionally, they point to the archaeological records, which strengthen the view that Semerkhet had a relatively short reign.

Semerkhet is well attested in archaeological records. His name appears in inscriptions on vessels made of schist, alabaster, breccia, and marble. His name is also preserved on ivory tags and earthen jar seals. Objects bearing Semerkhet's name and titles come from Abydos and Sakkara.

Semerkhet's serekh name is commonly translated as "companion of the divine community" or "thoughtful friend". The latter translation is questioned by many scholars, since the hieroglyph khet (Gardiner-sign F32) normally was the symbol for "body" or "divine community".

Semerkhet's birth name is more problematic. Any artefact showing his birth name curiously lacks any artistic detail of the used hieroglyphic sign: a walking man with waving cloak or skirt, a nemes head dress, and a long, plain stick in his hands. The reading and meaning of this special sign is disputed, since it doesn't appear in this form before association with king Semerkhet. Indeed, the hieroglyph of the cloaked man is extremely rare. It appears only twice in relief inscriptions depicting ceremonial processions of priests and standard bearers. Egyptologists such as Toby Wilkinson, Bernhard Grdseloff, and Jochem Kahl read Iry-Netjer, meaning "divine guardian". During the Old Kingdom period, this word is written with uniliteral signs of a netjer flag (Gardiner-sign R8) and a human eye (Gardiner-sign D4) nearby the ideogram of the man. Some contemporary ivory tags show the Nebty name written with the single eye symbol only. Thus, the scholars also read Semerkhet's throne name as Iry (meaning "guardian") and the Nebty name as Iry-Nebty (meaning "guardian of the Two Ladies"). This reconstruction is strengthened by the observation that Semerkhet was the first king using the Nebty title in its ultimate form. For unknown reason Semerkhet did not use the Nebuy title of his predecessor. It seems that he felt connected with the 'Two Ladies', a title referring to the goddesses Nekhbet and Wadjet, the patron deities of the Ancient Egyptians who were worshiped by all after the unification of its two parts, Lower Egypt, and Upper Egypt. The Nebty title in turn was thought to function as an addition to the Nisut-Bity title. His prenomen is Nisut-Bity-Nebty-Iry, nsw.t-bty-nb.ty-iry meaning, King of Upper and Lower Egypt, he of the two ladies, and he who belongs to them or He whom the two ladies guard.

Scribes and priests of the Ramesside era were also confused, because the archaic ideogram that was used during Semerkhet's lifetime was very similar to the sign of an old man with a walking stick (Gardiner sign A19). This had been read as Semsu or Sem and means "the eldest". It was used as a title identifying someone as the head of the house. Due to this uncertainty, it seems that the compiler of the Abydos king list simply tried to imitate the original figure, whilst the author of the Royal Canon of Turin seems to have been convinced about reading it as the Gardiner-sign A19 and he wrote Semsem with uniliteral signs. The Saqqara King List omits Semerkhet's throne name. The reason for that is unknown, but all kings from Narmer up to king Den also are missing their throne names.

Virtually nothing is known about Semerkhet's family. His parents are unknown, but it is thought that one of his predecessors, king Den, might have been his father. Possibly, Semerkhet was born to queen Betrest. On the Cairo Stone she is described as his mother, but definite evidence for that view has not yet been found. It would be expected that Semerkhet had sons and daughters, but their names have not been preserved in the historical record. A candidate as a possible member of his family line is his immediate successor, king Qa'a.

An old theory, supported by Egyptologists and historians such as Jean-Philippe Lauer, Walter Bryan Emery, Wolfgang Helck, and Michael Rice once held that Semerkhet was a usurper and not the rightful heir to the throne. Their assumption was based on the observation that a number of stone vessels with Semerkhet's name on them, originally were inscribed with king Adjib's name. Semerkhet simply erased Adjib's name and replaced it with his own. Furthermore, they point out that no high official and priest associated with Semerkhet was found at Sakkara. All other kings, such as Den and Adjib, are attested in local mastabas.