Sekhemkhet (also read as Sechemchet) was an ancient Egyptian king (pharaoh) of 3rd dynasty during the Old Kingdom. His reign is thought to have been from about 2648 BC until 2640 BC. He is also known under his later traditioned birth name Djoser-tety and under his Hellenized name Tyreis (by Manetho; derived from Teti in the Abydos king list). He was probably the brother or eldest son of king Djoser. Little is known about this king, since he ruled for only a few years. However, he erected a step pyramid at Saqqara and left behind a well known rock inscription at Wadi Maghareh (Sinai Peninsula).

The duration of Sekhemkhet's reign is believed to have been 6 to 7 years. The royal Turin Canon attributes 6 years of reign to Sekhemkhet,a figure also proposed by Myriam Wissa based on the unfinished state of Sekhemkhet's pyramid. Using his reconstruction of the Palermo Stone (5th dynasty), Toby Wilkinson assigns 7 years to this king. This figure is based on the number of year registers preserved in Cairo Fragment I, register V. Wilkinson states that "this figure is fairly certain, since the [king's] titulary begins immediately after the dividing line marking the change of reign.". Similarly, the Greek historian Manetho lists Sekhemkhet under the name of Tyreis and indicates that he reigned for 7 years. Nabil Swelim, by contrast, proposed a reign of 19 years, because he believed that Sekhemkhet might be the Tosertasis mentioned by Manetho. However, such a long reign is at odds with the unfinished state of the buried pyramid and this view is generally rejected by Egyptologists.


Clay seal from the island of Elephantine showing Sekhemkhet horus and nebty names.
Little is known about activities conducted during Sekhemkhet's reign. The only preserved documents showing Sekhemkhet are two rock inscriptions at Wadi Maghareh in the Sinai peninsula. The first one shows Sekhemkhet twice: once wearing the Hedjet crown, another wearing the Deshret crown. The second inscription depicts a scene known as "smiting the enemy": Sekhemkhet has grabbed a foe by its hair and raises his arm in attempt to clubb the enemy to death with a ceremonial sceptre. The presence of these reliefs at Wadi Maghareh suggests that local mines of copper and turquoise were exploited during Sekhemkhet's reign. These mines were apparently active throughout the early 3rd Dynasty since reliefs of Djoser and Sanakht were also discovered in the Wadi Maghareh.
Several clay seals presenting an unusual nebty name together with Sekhemkhet´s Horus name were found at the eastern excavation site on the island of Elephantine. The Egyptologist Jean Pierre Pätznik reads the nebty name as Ren nebty meaning The two ladies are pleased with his name. It is not entirely clear whether this is indeed Sekhemkhet´s nebty name or that of a yet unknown queen.