Attension is paid to the need / importance of an effective system of commercial banks' financial security and the negatives of its absence. It is noted that the formation of this system should be given daily attention of scientists and practitioners, government agencies, market regulators of banking services, self-regulatory organizations and commercial banks. The relationship and interdependence of liquidity of commercial banks and their financial security are determined. The importance of commercial banks' liquidity in ensuring the financial security of banking institutions is emphasized. Based on a critical analysis of existing approaches in the economic literature, the author's vision of the essence of financial security of commercial banks, as well as quantitative and qualitative characteristics of its components. The nature of risks of loss / insufficient (negative) / excess / unbalanced liquidity is considered in detail and the negative consequences of their manifestation for the functioning of commercial banks and the banking sector of the national economy in general are revealed. The relationship and interdependence of risks of loss / imbalance / insufficiency / excess liquidity of commercial banks and other risks associated with banking activities are illustrated. The place and role of liquidity of commercial banks in ensuring their financial security and the importance of their liquidity for various stakeholders are determined. The author's vision of indicators of liquidity contribution to financial security of commercial banks is offered. It is concluded that the liquidity of commercial banks directly affects such components / varieties of their FB as resource, deposit, credit, currency, investment and debtsecurity, security of settlement operations and security of income and expenses, as well as the level of financial security of commercial banks in general.