4-Chlorophenylhydrazine is primarily used in the synthesis of various organic compounds, particularly in the production of pharmaceuticals and dyes. It serves as a key intermediate in the preparation of heterocyclic compounds, which are essential in the development of drugs targeting a range of medical conditions. Additionally, it is employed in the manufacture of azo dyes, contributing to the vibrant colors in textiles and other materials. Its role in chemical research is also significant, as it aids in the study of reaction mechanisms and the development of new synthetic pathways.