The article summarizes the theoretical foundations of the emergence and development of crisis phenomena in economic systems and the peculiarities of their manifestation at the macro level. It is emphasized that the economic crisis represents a complexly structured and multifactorial system of relationships with the external environment, as well as a multicomponent internal structure, which complicates the process of its study. It has been established that in the scientific literature, the position of considering the crisis as an unfavorable situation in the development of individual economic systems prevails, however, there are different approaches to the definition of this concept, as well as the predominance of its favorable and unfavorable characteristics. The theoretical principles of economic science regarding the understanding of the essence of economic crises are summarized and the following approaches are highlighted: classical, rational combination of market self-regulation and state regulation, intermediary-behavioral. It was established that the crisis was viewed as a factor of negative impact on the economy, caused by the instability of the markets, and also as a process that requires prompt response in order to stabilize the crisis situation and neutralize its consequences. Attention is drawn to such a characteristic of the crisis as its duration, which depends on the state of the external and internal environment of the functioning of economic systems, which requires a detailed identification of its factors and vectors of influence. The existing approaches to the definition of the concept of «crisis» are systematized and two main groups are distinguished, one of which considers the crisis as a negative phenomenon, and the second – as a turning point in the life cycle of the enterprise, as an impulse for further development, which can have both negative and positive effects. consequences. On the basis of which, a conclusion was made about the need for the management of any enterprise to monitor its functioning environment in order to identify possible causes of crises and their monitoring. It is substantiated by the reasons for the probability of a crisis at the enterprise level due to changes in the external and internal environment of its functioning. It is proposed to distinguish the concept of «crisis» as a state of the enterprise, which involves its disorganization, and «crisis process» as an unstable, dynamic process of changing the values of the main parameters of its internal and external environment. The author's approach to the examination of the crisis involves considering the state of the enterprise at the breaking point, which is determined by the contradictions between the internal and external environment, which, in the absence of the possibility of their resolution, can cause irreversible consequences for it functioning system. Regarding the understanding of the crisis process, it should be considered as a process that changes the state of the enterprise due to the influence of contradictions between the internal and external environment, which constantly changes the values of their main parameters and has a continuous, dynamic, unstable, cyclical nature. It is argued that the crisis process begins to arise if the internal state of the enterprise does not match its macro environment, which can lead to its possible liquidation. The need to study the crisis according to the stages of the crisis process is substantiated, which will allow to determine the bifurcation points at which the enterprise becomes unstable, according to the periods of the development of the crisis process, and to distinguish the following types of crisis: strategic, liquidity, insolvency, critical. Key words: crisis, crisis process, economic system, enterprise, crisis duration, bifurcation points.