The Sumerians were a civilization that lived in ancient Mesopotamia (modern-day Iraq) from around 3500 BC to 1900 BC. The Sumerians were polytheistic, meaning they believed in many gods and goddesses. Some of the most important Sumerian gods included Anu (the god of the sky), Enlil (the god of the air and the storm), Enki (the god of water and wisdom), and Inanna (the goddess of love and war).