Metchnikowin is a 26-residue antimicrobial peptide of the fruit fly Drosophila melanogaster that displays both antibacterial and antifungal properties.

[2] Metchnikowin is named after Russian immunologist Élie Metchnikoff, one of the founders of modern immunology.

Metchnikowin has microbicidal activity against the gram-negative bacterium Escherichia coli and filamentous fungus Neurospora crassa at nanomolar concentrations.

[1] It is also one of the most abundant defence peptides in D. melanogaster following infection by the entomopathogenic fungus Beauveria bassiana.

[3] Proline-rich peptides such as metchnikowin can bind to microbe ribosomes, preventing protein translation.