<jats:title>Abstract</jats:title><jats:p>The analysis of volatiles from bacterial cultures revealed long‐chain aliphatic nitriles, a new class of natural products. Such nitriles are produced by both Gram‐positive Micromonospora echinospora and Gram‐negative Pseudomonas veronii bacteria, although the structures differ. A variable sequence of chain elongation and dehydration in the fatty acid biosynthesis leads to either unbranched saturated or unsaturated nitriles with an ω−7 double bond, such as (<jats:italic>Z</jats:italic>)‐11‐octadecenenitrile, or methyl‐branched unsaturated nitriles with the double bond located at C‐3, such as (<jats:italic>Z</jats:italic>)‐13‐methyltetradec‐3‐enenitrile. The nitrile biosynthesis starts from fatty acids, which are converted into their amides and finally dehydrated. The structures and biosyntheses of the 19 naturally occurring compounds were elucidated by mass spectrometry, synthesis, and feeding experiments with deuterium‐labeled precursors. Some of the nitriles showed antimicrobial activity, for example, against multiresistant Staphylococcus aureus strains.