The article is devoted to analysis of the principle of patient autonomy and informed consent. The principle of patient autonomy is a fundamental principle of modern bioethics in the developed countries of the world. This principle was proclaimed as a result of the change in the medical-social paradigm and of the departure from the paternalistic model of the doctor-patient relationship to the model of the active patient in the provision of medical care. The autonomy of patients is connected, firstly, with freedom in general as a manifestation of independence from someone's controlling influences, and, secondly, with free will as the ability of the subject to deliberate action. Informed consent was originally formed as a bioethical principle aimed at protecting patients. Today, this principle is one of the legal mechanisms aimed at implementing the principle of patient autonomy. The author analyzes the relationship between the principle of patient autonomy and informed consent and concludes that there is a systemic relationship between them. In addition, it addresses the general requirements for informed consent in foreign countries and domestic law; it defines the place of informed consent in the system of legal facts; it analyzes judicial practice in which informed consent acts as a subject of legal analysis; determined bioethical and legal significance of informed consent and analyzes further transformation of its ethical and legal entities to enhance its formal legal value.