Final answer:
Alexander the Great's empire included the Nile River in Egypt and the Tigris and Euphrates Rivers in Mesopotamia, areas that were central to early civilizations.
Step-by-step explanation:
The major rivers that were centers of the first civilizations included in Alexander the Great's empire were the Nile River in Egypt and the Tigris and Euphrates in Mesopotamia. The Nile River Valley was the cradle of Egyptian civilization, known for its predictable flooding, which provided fertile land for agriculture. Mesopotamia, sometimes referred to as the Fertile Crescent, is where early urban centers and empires like Sumeria, Babylon, and Assyria thrived due to the fertile floodplains of the Tigris and Euphrates Rivers. Alexander's conquests included Egypt, where he founded the city of Alexandria, and stretched across the Persian Empire, which already encompassed Mesopotamia.