Mycolic acid, also known as trehalose dimycolate, is a key component of the outer layer of the cell wall of mycobacteria, making it a target for drug development. There are several synonyms for mycolic acid, including cord factor, wax D, mycoside, and mycocerosic acid. These terms are all used interchangeably to describe the unique, waxy lipid that gives mycobacteria their characteristic tough cell wall. Mycolic acid is important for the pathogenicity of mycobacteria, allowing them to resist host immune defenses and persist in the body for long periods. By targeting mycolic acid synthesis or function, new drugs could help combat tuberculosis and other mycobacterial diseases.