An inbred maize line, designated PH51K, the seeds and plants of inbred maize line PH51K, methods for producing a maize plant, either inbred or hybrid, produced by crossing the inbred maize line PH51K with another maize plant, and seed and plants produced therefrom. The invention also relates to methods for producing a modified PH51K maize plant that comprises in its genetic material one or more transgenes or backcross conversion genes and to the transgenic and backcross conversion maize plants produced by these methods. This invention also relates to methods for producing other inbred and hybrid maize lines derived from inbred maize line PH51K and to the inbred and hybrid maize lines so produced.