10-十一烯酸是一种含11个碳原子的不饱和脂肪酸，结构式CH₂＝CH(CH₂)₈COOH。

室温左右，十一烯酸为无色有光泽、有水果特殊气味的液体，或无色具腐败气味的潮解固体。微溶于水，溶于乙醇、乙醚。低毒，有轻微的刺激性。

Undecylenic acid is a synthetic unsaturated fatty acid. It is prepared from the natural product, ricinoleic acid, present in castor oil. Undecylenic acid is produced by cracking castor oil at high temperature and pressure. It is the common name of 10-undecenoic acid, abbreviated (CH₂=CH(CH₂)₈COOH), and has two functional groups, a terminal alkene at one end, and a carboxylic acid at the other. It has use in synthetic chemistry and is used in the manufacture of pharmaceuticals, personal hygiene products, cosmetics, and perfumes. It also used as a topical antifungal agent.