'Cutting out' areas of a face..

Okay, so what I want to do is cut a circle out of the face of a cylinder, which has been converted to a mesh. Is there a way of drawing a circle onto the face and making blender cut that area out? I know you can do it with bezier circles, but now it is a mesh I’m not sure how that would work, as the ‘face’ is now made out of many tris…

Does anyone have any ideas? Thanks in advance.