The article analyzes and summarizes the positions of the Supreme Court on the ground for necessary defence. It is noted that the Supreme Court has identified two elements of the ground for necessary defence (the commission of a socially dangerous trespass and the need to immediately avert or stop it) and has repeatedly referred to the interpretation of various aspects of each of them. The article mentions various definitions of “socially dangerous trespass” provided by the Supreme Court in its rulings. It is noted that the Supreme Court has not addressed the possibility of recognizing a socially dangerous act of an insane person or a person under the age of criminal liability as a socially dangerous trespass as a ground for necessary defence, but in one of its rulings it admitted that such a trespass was committed by a mentally ill victim. The author mentions the conclusion of the Supreme Court that the right to necessary defence cannot arise against lawful acts of another person, even if such acts cause damage to legally protected interests. It is mentioned that, in general, the Supreme Court does not recognize provoked violence as a trespass within the meaning of Article 36 of the Criminal Code of Ukraine, but the exception is when the degree of provoked violence is clearly higher than what a person could have predicted. It is noted that the Supreme Court identifies the objective reality of a socially dangerous trespass as its mandatory characteristic for necessary defence. The author quotes the Supreme Court’s explanation of when it is necessary to immediately avert or stop a socially dangerous trespass. The conclusions of the Supreme Court regarding the time limits of the right to necessary defence are analyzed. In particular, the Supreme Court identifies the initial and final moments of lawful defence. The ruling is mentioned, in which the Supreme Court reminds of the legal prohibition to take into account the possibility of a person to avoid a socially dangerous trespass or to request assistance of other persons or authorities when deciding on the existence or absence of a state of necessary defence.