In Islam, since accountability for actions is tied to being intelligent, the addressee of commands and prohibitions is a rational individual. However, while a person may have completed the necessary stages of physical development in a healthy manner, they may not have progressed to the stages that lead to mental maturity. When the necessary stages of mental development are not met for various reasons, a person's capacity to act is negatively affected, and therefore, various levels of mental illness can be observed that can compromise a person's responsibilities. From this perspective, the question of whether mentally ill individuals fall within the scope of the concept of "personhood" in the legal system and whether they are entitled to rights and obligations emerges as a matter requiring clarification. The purpose of this study is to explain what mental illness is, define the "person," examine the mentally ill from the perspective of Islamic personal law, and ultimately evaluate them in terms of religious practices, legal, and criminal proceedings.