The Sed Festival, or the King's Jubilee, was a festival of rejuventation and reassertion of the king's sovereignty and possession of the land of Egypt. Though the exact origins of this festival are somewhat obscure, it is possible that the need for this festival is rooted in the very archaic times. Times when it could have been necessary to remove a king showing signs of failing powers by death.

The Sed Festival renewed the king's vigour, as well as reasserting his power over both Upper and Lower Egypt. This rejuvenation of the king was of national importance and the entire nation was deeply concerned with the celebration of these important rites. Usually the festival took place thirty years after the king's assumption of power, but evidence from the Palermo Stone leads to the belief that the Sed festival was celebrated by some of the archaic kings repeatedly and at much shorter intervals.

To celebrate the festival, special buildings were erected, most notably a Throne Room and a Robing Room in which the king changed his dress and insignia according to the double rites connected with the two lands, Upper and Lower Egypt. Most importantly was the Heb-Sed Court which was flanked on both sides with chapels of the gods of each nome or province in Upper and Lower Egypt. In the open space between the two rows of shrines, the king, attired alternately in the insignia of Upper and Lower Egypt, ran a ritual race around a course which was called "the field". The king would round the boundaries of the field four times as the ruler of Upper Egypt and fourt times as the ruler of Lower Egypt.

Other ceremonies also took place during the Sed festival, such as the act of homage to the king by the "Great Ones of Upper and Lower Egypt". This festival was also an occasion for the issue of commemorative objects, including stone vases bearing the king's titulature.

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Sources:
Archaic Egypt - W.B. Emery
Egypt Before the Pharaohs - Michael Hoffman
A History of Ancient Egypt - Nicolas Grimal