Besor (Hebrew: נחל הבשור‎, Nahal HaBesor) is a wadi in southern Israel. The stream begins at Mount Boker (near Sde Boker), and spills into the Mediterranean Sea near Deir al-Balah in the Gaza Strip, where it is called Wadi Gaza. Further upstream it is marked as Wadi esh-Shallaleh on the 1878 Survey of Western Palestine map. The stream is the largest in the northern Negev, and together with its largest tributaries, the Grar and Beersheba streams, reaches as far east into the desert as Sde Boker, Yeruham, Dimona and Arad/Tel Arad. The Gaza section of the Coastal Aquifer the only significant source of water in the Gaza Strip.