二十二碳六烯酸（英语：Docosahexaenoic Acid，DHA）是有六个双键的多元不饱和脂肪酸（C₂₂H₃₂O₂），是一种ω-3必需脂肪酸。

鱼油含有丰富的DHA。大部分在鱼类和其他生物的DHA起源于光合和异养微藻。在食物链越上层的生物，DHA份量越多。DHA在商业上也可以从微藻Crypthecodinium chonii和裂殖壶菌属（Schizochytrium）提炼出。使用微藻来生产的DHA是素食。而大多数的动物很少通过代谢生产DHA，但是足够的DHA能透过吃α-亚麻酸，一种ω-3脂肪酸，生产出来，这些动物包括人类。

Docosahexaenoic acid (DHA) is an omega-3 fatty acid that is a primary structural component of the human brain, cerebral cortex, skin, sperm, testicles and retina. It can be synthesized from alpha-linolenic acid or obtained directly from maternal milk (breast milk), fish oil or algae oil. DHA's structure is a carboxylic acid (-oic acid) with a 22-carbon chain (docosa- is Greek for 22) and six (hexa-) cis double bonds (-en-); with the first double bond located at the third carbon from the omega end. Its trivial name is cervonic acid, its systematic name is all-cis-docosa-4,7,10,13,16,19-hexa-enoic acid, and its shorthand name is 22:6(n-3) in the nomenclature of fatty acids.