An airfoil comprises one or more internal cooling circuits. The cooling circuits can be fed with a flow of cooling fluid from one or more cooling air inlet passages in fluid communication with the cooling circuits. The cooling circuits can further comprise a leading edge cooling circuit defined by a supply passage, a pin bank passage divided into one or more sub-circuits by pin banks disposed within the pin bank passage, and at least first and second cooling passages. The cooling circuits can provide the cooling fluid flow within the airfoil to cool the airfoil, as well as provide a cooling fluid to a plurality of film holes to create a cooling film on the external surface of the airfoil.