The Greater Zab River is one of the main tributaries of the Tigris River. The river runs in the central northern part of Iraq, and then joins the Tigris River south of Mosul city, in the northern central part of Iraq. It has four main tributaries, called; Shamdinan, Haji Beg, Rawandooz and Khazir – Gomal rivers, beside tens of small tributaries and ephemeral streams, which drain directly in the main river. The studied catchment area of the Greater Zab River; in Iraq attains about 13708 Km2, and extends in the northern and northeastern parts of Iraq, and farther more in Turkey and Iran. The basin of the river is divided into four sub-basins of the aforementioned tributaries and a fifth one, which includes the catchment area that drain directly in the Greater Zab River. The widths of the five sub-basins range from (1.54 – 6.19) Km, whereas their lengths range from (41.4 – 108.3) Km. The catchment's areas of the Greater Zab River and its four tributaries are covered mainly by carbonate rocks of many formations, which range in age from Triassic to Pliocene – Pleistocene, beside igneous and metamorphic rocks, especially in the northeastern parts. Moreover, fine clastics of Injana and Mukdadiya formations, coarse clastics of Bai Hassan Formation, and marl, limestone and gypsum of the Fatha Formation cover considerable area. Through the courses of the Greater Zab River and its four tributaries, they cross tens of anticlines, almost perpendicularly; some of them have gorge forms, forming 34 water gaps and 15 air gaps, in the studied area. The geomorphology and morphotectonics of the Greater Zab River basin are studied. Six Morphometric indices have determined in this study, using ArcGIS technique, which indicated High, Moderate, Very High, Very High and High relative tectonic activity for the five sub-basins, respectively. Geomorphological and basin drainage maps of the studied area are prepared, too.