Used primarily in the synthesis of dyes and pigments, 3-Hydroxyphthalic anhydride serves as a key intermediate. It is also employed in the production of certain polymers and resins, enhancing their thermal stability and mechanical properties. In the pharmaceutical industry, it acts as a building block for creating active pharmaceutical ingredients (APIs). Additionally, it finds application in organic synthesis for constructing complex molecules due to its reactive anhydride group. Its versatility makes it valuable in various industrial and research contexts.