4-Aminonicotinic acid is an organic compound featuring a pyridine ring substituted with an amino group at the 4-position and a carboxylic acid group at the 3-position. It is a white to off-white crystalline powder. This structure makes it a versatile heterocyclic building block. Its primary and most significant application is in the pharmaceutical industry as a key intermediate. It is widely used in the synthesis of various active pharmaceutical ingredients (APIs), particularly those belonging to the vitamin B3 (niacin) derivative family and other nicotinic acid-based drugs. It serves as a crucial precursor for compounds with potential biological activities. Beyond its role as a pharmaceutical intermediate, 4-aminonicotinic acid is also employed in organic synthesis and material science research due to its bifunctional nature (amine and carboxylic acid), which allows for further derivatization. It is considered a hazardous substance and requires careful handling, as it may cause skin and eye irritation.