Egypt has the oldest continuously existing civilization in the world. Most scholars believe that the Egyptian kingdom was first unified in about 3100 bc. Egypt maintained its independence and unity for many centuries thereafter. It suffered disunity now and then and experienced brief periods of foreign domination by the Semitic Hyksos in the 17th and 16th centuries bc, the Assyrians in the 7th century bc, and the Persians in the 6th and 5th centuries bc before the arrival of Macedonian conqueror Alexander the Great in 332 bc. Alexander made Egypt a part of his vast empire.

The First Cataract at Aswan, where the riverbed is turned into rapids by a belt of granite, was the country's only well-defined boundary within a populated area. To the south lay the far less hospitable area of Nubia, in which the river flowed through low sandstone hills that left a very narrow strip of cultivable land. Nubia was significant for Egypt's periodic southward expansion and for access to products from farther south. West of the Nile was the arid Sahara, broken by a chain of oases some 125-185 miles (about 200-300 kilometres) from the river and lacking in all other resources except for a few minerals. The eastern desert, between the Nile and the Red Sea, was more important, for it supported a small nomadic population and desert game, contained numerous mineral deposits including gold, and was the route to the Red Sea.

Alexander’s empire broke up after his death in 323 bc. One of his generals, Ptolemy, became ruler of Egypt, and in 305 bc he assumed the title of king. Ptolemy founded the Ptolemaic dynasty. Under these rulers, Egypt became a center of the Hellenistic world that is, the vast region, encompassing the eastern Mediterranean basin and the Middle East, in which Greek culture and learning were preeminent from Alexander’s conquest until the 1st century bc. Although the Ptolemies preserved many native traditions, they remained unpopular because they kept Egyptians from important governmental posts. The Romans conquered Egypt in 30 bc, ruling it as a province of their empire for the next several centuries. One of the first countries to be exposed to Christianity, Egypt became predominantly Christian by the end of the 3rd century ad. In 395, when the Roman Empire was divided, Egypt was included in the Eastern Roman Empire, later called the Byzantine Empire. By the 5th century a bitter religious dispute over the nature of Christ, involving a doctrine known as Monophysitism, had developed in the Eastern church. This dispute pitted the Coptic Church, Egypt’s indigenous Christian body, and other Middle Eastern Christians against the Byzantine rulers. The conflict weakened Byzantine rule in Egypt and helped open the way to the conquest of Egypt by an Arab army in 641. Many Egyptians welcomed the Arab conquerors as liberators from foreign taxation and religious persecution.