Egypt, Ancient, great civilization that arose along the banks of the Nile River more than 5,000 years ago.
Egypt became a single nation c.3100 B.C., when the kingdoms of Upper (southern) and Lower (northern) Egypt were unified by Menes, who founded a capital at Memphis, about 12 mi (18 km) from what is now Cairo. The state inaugurated by Menes, called the Old Kingdom, lasted until c.2200 B.C. It was during this period that the great pyramids of Giza were built. The largest was constructed under the reign of the pharaoh Cheops, dates from about 2500 B.C. It was during the Old Kingdom that writing and paper were developed, and Egyptian commerce flourished.
The fall of the Old Kingdom resulted in two centuries of chaos, ending c.2100 B.C. with the establishment of the Middle Kingdom, whose capital was at Thebes, in southern (Upper) Egypt. The Middle Kingdom flourished until the 18th century B.C. when the country fell before the Hyksos, Asiatic nomads. The rule of the Hyksos marked the second intermediate period (1786– c.1570 B.C.). A native uprising under the princes of Thebes led to the gradual reconquest of Egypt from the Hyksos, and the foundation of the New Kingdom in about 1570. It was during the XVIII dynasty (1570-c. 1352 B.C.) that Egyptian civilization reached its height. Thebes and Memphis became the world's greatest centers of commerce and culture, and Egyptian rule extended from the Sudan to the Euphrates River.
Egyptian power began to decline after the war with the Hittites in Syria (1296–1279 B.C.). Ramses ΙII (d. 1167 B.C.) was the last great ruler of the New Kingdom. Following his reign, Egyptian politics were dominated by divisive intrigue, civil war, and weak and ineffective leadership. In 525 B.C. Persia conquered and annexed Egypt, and when Alexander the Great overthrew Darius IIΙ of Persia (333 B.C.), he was welcomed into Egypt, which became part of his empire. Upon the death of Alexander, Ptolemy, one of his generals, established a new dynasty in Egypt. The first Ptolemy (r.305–285 B.C.) built the great museum and library at Alexandria. The Ptolemy dynasty lasted until 30 B.C., when Cleopatra died and Egypt was annexed by Rome.
Christianity was introduced in Egypt in the 2nd, 3rd, and 4th centuries, and around A.D. 390 the country became part of the Byzantine Empire. With the Arab invasion of A.D. 640, the population was Arabized culturally and linguistically, and since then Egypt has been part of the Muslim world.