3,6,9,12,15-Octadecapentaenoic acid, (3Z,6Z,9Z,12Z,15Z)-, is a polyunsaturated fatty acid (PUFA) with five cis-conjugated double bonds, structurally related to omega-3 fatty acids. Its extended unsaturation confers high reactivity and potential utility in lipid research, particularly in studies of membrane fluidity, signaling pathways, and eicosanoid biosynthesis. The compound’s precise double-bond configuration makes it valuable for investigating structure-activity relationships in bioactive lipids. It may also serve as a precursor for specialized pro-resolving mediators (SPMs) or as a reference standard in analytical chemistry. Due to its instability, handling requires inert atmospheres and low-temperature storage to prevent oxidation. Suitable for controlled experimental applications in biochemistry and nutrition research.