Nebka (meaning "Lord of the ka") is the throne name of an ancient Egyptian pharaoh of the Third Dynasty during the Old Kingdom period, in the 27th century BCE. He is thought to be identical with the Hellenized name Νεχέρωχις (Necherôchis or Necherôphes) recorded by the Egyptian priest Manetho of the much later Ptolemaic period.

Nebka's name is otherwise recorded from the near contemporaneous tomb of a priest of his cult as well as in a possible cartouche from Beit Khallaf, later New Kingdom king lists and in a story of the Westcar Papyrus. If the Beit Khallaf seal impression is indeed a cartouche of Nebka, then he is the earliest king to have thus recorded his throne name, otherwise this innovation can be ascribed to Huni.

Nebka is thought by most Egyptologists to be the throne name of Sanakht, the third or fourth ruler of the Third Dynasty, who is sparsely attested by archaeological evidence and must have had only a short reign. Older hypotheses followed two New Kingdom sources which credit Nebka with founding the Third Dynasty, a view that is now believed to contradict the archaeological evidence. The tomb of Nebka has not been located with any certainty and three locations have been proposed: a mastaba in Beit Khallaf attributed to Sanakht by John Garstang, a mudbrick structure in Abu Rawash seen as the tomb of Nebka by Swelim and Dodson, and the Unfinished Northern Pyramid of Zawyet El Aryan.

The earliest source for Nebka's name is the mastaba tomb of the late Third Dynasty high official Akhetaa who, among other positions, held that of "priest of Nebka". The exact location of Akhetaa's mastaba is now lost, hindering further research. It may be near Abusir, where some relief-bearing blocks from the tomb were found re-used as construction material.

The next oldest source is found in a story recorded on the Westcar Papyrus which dates to the Seventeenth Dynasty, but which was likely first written during the late Middle Kingdom period, possibly at the end of the Twelfth Dynasty. There, a king Nebka is cited in the story known as “Nebka and the crocodile”, which pertains to adultery and the typical sort of punishment for that during the Old Kingdom. The story throws a positive light on the personality of king Nebka, who is depicted as a strict but lawful judge. He punishes mischief and unethical behavior, in this case punishing the betrayal of an unfaithful wife with the death penalty. The passage involving Nebka starts after a magician, Ubaoner, throws a commoner who had an affair with Ubaoner's wife to a crocodile, who swallows him for seven days:

During these seven days Ubaoner is received by pharaoh Nebka for an important audience. After the audience Ubaoner invites Nebka to visit his house with the words: “May thy majesty proceed and see the wonder that has happened in the time of thy majesty [... text damaged ...] a commoner.” Nebka and Ubaoner walk to the lake where Ubaoner orders the crocodile to come out of the water and to release the commoner. When king Nebka sees that he says: “This crocodile is dangerous!” But Ubaoner bends down and touches the crocodile and immediately it becomes a figurine of wax again. Then Ubaoner gives a report to Nebka about the affairs. Nebka tells the crocodile: “Take away what is yours!” and the animal grabs the commoner and then disappears. The wife of Ubaoner is brought to Nebka too, and the pharaoh sentences her to death. She is brought to a place east of the palace and burnt alive. Her ash is thrown into the Nile.

The subsequent historical sources date to the Nineteenth Dynasty: the Royal Table of Saqqara mentions a Nebkara close to the end of the Third Dynasty as the direct successor of Sekhemket and predecessor of Huni. This Nebkara is likely a variant of the name Nebka. The near contemporaneous Abydos King list and Turin canon record a king Nebka, this time as the founder of the Third Dynasty.

Finally, a king Necherôchis is listed as the founder of the Third Dynasty in the Aegyptiaca, a history of Egypt written in the 3rd century BCE during the reign of Ptolemy II (283–246 BCE) by an Egyptian priest, Manetho. No copies of the Aegyptiaca have survived to this day and it is now known only through later writings by Sextus Julius Africanus and Eusebius, themselves quoted by the Byzantine scholar George Syncellus. According to these sources, the Aegyptiaca gave Necherôchis as the predecessor of Sesorthos or Tosorthros, both names being widely held to refer to Djoser as the Aegyptiaca credits Sesorthos with the invention of stone architecture. Necherôchis (Eusebius) or Necherôphes (Africanus), both likely Hellenized forms of Nebka, is said to have faced a rebellion of Libyans during his reign, but "when the moon waxed beyond reckoning, they surrendered in terror". Africanus further credits Necherôphes with 28 years of reign.