The Sumerians, who settled in southern Mesopotamia (modern-day Iraq), established the world's first known cities around 4000-3500 BCE, including Uruk and Ur, with advanced systems of writing (cuneiform), mathematics, and governance that define urban civilization. While Egyptians and Chinese also developed early civilizations, the Sumerian city-states predate them. "Mesopotamians" is a broader regional term that includes Sumerians but also later cultures like Babylonians and Assyrians.