Octanoic acid is a straight-chain saturated fatty acid that is heptane in which one of the hydrogens of a terminal methyl group has been replaced by a carboxy group. Octanoic acid is also known as caprylic acid. It has a role as an antibacterial agent, a human metabolite and an Escherichia coli metabolite. It is a straight-chain saturated fatty acid and a medium-chain fatty acid. It is a conjugate acid of an octanoate.