A national bank in the United States is a financial institution chartered and regulated federally by the Office of the Comptroller of the Currency rather than by state banking authorities. These institutions are required to maintain membership in the Federal Reserve System and have their customer deposits insured up to statutory limits by the Federal Deposit Insurance Corporation. National banks form the backbone of the American financial architecture, providing nationwide retail banking, commercial lending, and treasury services while adhering to strict federal capital adequacy and liquidity reserve standards.