In order to protect children from risks associated with bad parenting, some philosophers have recommended that all parents be licensed, in much the same way in which drivers of motor vehicles and many professionals, such as physicians, are licensed. In this chapter, we clarify what parental licensing is, describe philosophical theories about it, and assess these theories in terms of how well they deal with problems of discrimination in parental licensing. While much of our discussion focuses on biologism, the privileging of biological parenthood over non-biological forms of parenthood, we also touch on other forms of discrimination that parental licensing can cause or exacerbate, such as classism, sexism, homophobia, racism, and ableism. Our view is that any adequate proposal in favor of parental licensing must take worries about discrimination seriously. Unfortunately, most philosophical proposals fail to do so.