Abstract: An infinitely adjustable knife sharpener apparatus is provided. The apparatus comprises a clamping mechanism having a first clamp member and a second clamp member for securing a knife blade therebetween. At least one infinitely adjustable guide rod assembly is also included. For example, an infinitely adjustable guide rod can be employed to determine an angle to which a knife blade is sharpened. Additionally, or alternatively, an infinitely adjustable guide loop can be included to determine an angle to which the knife blade is sharpened. Further, the apparatus is adjustable via a plurality of apertures in at least one of the first and second clamp members. Repositioning the guide rod assembly along a length of the first and/or the second clamp members changes the sharpening angle of the apparatus. A swivel block can also be included to facilitate foldability of the guide rod assembly.