4-Hydroxyphenylarsonic acid is an organoarsenic compound primarily used as a chemical intermediate in the synthesis of other organoarsenic compounds, such as roxarsone (3-nitro-4-hydroxyphenylarsonic acid), which is employed in animal feed additives, especially for poultry production, to promote growth, improve feed efficiency, and control certain parasites and pathogens like coccidia. This contributes to healthier livestock and increased weight gain. Due to concerns about arsenic residues in meat and environmental impact, the use of its derivatives like roxarsone has significantly declined in many regions and is banned in some countries. The compound itself is also utilized in limited research applications for developing antimicrobial agents or other bioactive organoarsenic substances.