The Jezreel Valley, in Arabic Marj Ibn Āmir (مرج إبن عامر), also known as the Valley of Megiddo, is a large fertile plain and inland valley in the Northern District of Palestine. It is bordered to the north by the highlands of the Lower Galilee region, to the south by the Samarian highlands, to the west and northwest by the Mount Carmel range, and to the east by the Jordan Valley, with Mount Gilboa marking its southern extent. The largest settlement in the valley is the city of Afula, which lies near its center.

The valley once acted as the channel by which the Mediterranean Sea, at the north-western end of the valley, connected to the Sea of Galilee, the Jordan Valley and ultimately to the Dead Sea. About two million years ago, as the land between the Mediterranean Sea and the Jordan Rift Valley rose, this connection was lost, and the periodic floods from the Mediterranean Sea ceased. This resulted in the Dead Sea no longer having a connection to the ocean, and over time, due to greater evaporation than precipitation plus surface water inflow, it has become heavily saline. The Sea of Galilee, on the other hand, consists of fresh water.