5-Carboxy-8-hydroxyquinoline is a heterocyclic organic compound featuring both a carboxylic acid and a phenolic hydroxyl group on a quinoline scaffold. This bifunctional structure makes it a versatile chemical building block. Its primary application is in the synthesis of metal chelating agents and pharmaceutical intermediates. The molecule is a key precursor for the preparation of clioquinol (5-chloro-7-iodo-8-hydroxyquinoline), a historically used antimicrobial and antiprotozoal agent. Furthermore, derivatives of 8-hydroxyquinoline are extensively researched for their biological activities, including antimicrobial, anticancer, and metal-chelating properties, particularly in the context of neurodegenerative diseases like Alzheimer's. As a synthetic intermediate, it is employed in the development of more complex quinoline-based compounds for medicinal chemistry and materials science. It serves as a classic example of a functionalized heterocyclic scaffold in organic synthesis.