Loop peptides are a class of ribosomally synthesized and post-translationally modified natural products that exhibit a diverse set of relevant activities, including bacterial growth inhibition, receptor antagonist, and enzyme inhibition. Genomic mining strategies have contributed to the discovery of novel loop peptides and also novel peptide-producing microorganisms from this group. However, little is known about the production of loop peptides by the microbiota of the rumen ecosystem. In this review, we have gathered updated information on the characteristics, structures and classification of loop peptides, as well as the biosynthesis and function of these molecules.