Horseshoe kidney (HSK) is the most common renal fusion, which is characterized by three anatomic anomalies: ectopia, malrotation and vascular changes. Patients with HSK are prone to a variety of complications, genitourinary and non-genitourinary. In this paper, the anatomy of HSK is delineated with a great emphasis on its blood supply. After reviewing the literature, the arterial supply patterns found by each author were categorized according to the classification system proposed by Graves. The majority of HSKs were found to be supplied by renal arteries derived from the abdominal aorta below the isthmus or by vessels originating from the common iliac arteries. In addition, the abnormalities associated with HSK are highlighted and classified in anatomical variations, congenital anomalies as well as in pathologic conditions related to HSK.