Heneicosylic acid, or heneicosanoic acid, is the organic compound with the formula CH3(CH2)19CO2H.

It is the straight-chain 21-carbon saturated fatty acid.

It has shown relevance in the production of foams, paints, and related viscous materials.

[1] A laboratory preparation involves permanganate oxidation of 1-docosene (CH3(CH2)19CH=CH2).

This article about an organic compound is a stub.