Cyprinus carpio L., 1758 - apart from its commercial importance, this fish is also considered an ideal experimental model for studying different branches of biology. The liver of fish serves as a good indicator for identifying the toxicity of components of the biosystem. Ultrastructural data on the structure of the liver of this fish are incomplete. This study is devoted to the study of the ultrastructure of the liver of common carp using light and electron microscopy methods. The liver capsule is composed of the epithelial layer and connective tissue elements. The wall of the sinusoids consists of endothelium, which in turn, connect to each other through intercellular connections. Hepatic stellate cells, also known Ito cells, are observed between sinusoids and hepatocytes. The membranes of hepatocytes are connected to each other by desmosomes. Intracellular canaliculi are present in the cytoplasm of the hepatocyte. They are formed as a result of intussusceptions of the hepatocyte membrane. There are numerous microvilli leading to the lumen of the intracellular canaliculi. The biliary ductule wall consists of a epithelial cells and has a elongated nucleus. Biliary ductules wall widen and open into the bile ducts. They are composed of four layers. A comparative ultrastructural characterization of the carp liver with other fish species and vertebrate animal livers was also carried out. The obtained results can be used in the study of ultrastructural changes occurring in the body of living organisms, including fish, during toxic effects.