A hair trimming guide offers four edges; a first curved edge, a second curved edge, a first straight edge, and a second straight edge. These four edges allow a person to easily trim or shape their hair, such as a beard, by following the edges of the hair trimming guide. The curved edges are used when a person wants a curved outline to their beard, such as along the cheeks. If no curved outlines are desired, a user can simply trim with the straight edges. For use with larger or smaller facial areas, the hair trimming guide can be offered in multiple sizes, providing a larger size for larger facial areas and a smaller size for smaller facial areas, especially around the nose and mouth. The hair trimming guide is flat and smooth which enables it to be pressed against a user's face without causing discomfort.