Geneticin G418 is an aminoglycoside antibiotic used for selection and maintenance of cells that contain the neomycin phosphotransferase resistance gene (neo/kanR). It is applied in mammalian cell culture, yeast, protozoa, and certain bacteria such as E. coli to enrich for plasmid-bearing transformants or stable integrants carrying the appropriate resistance marker.

G418 inhibits protein synthesis by targeting ribosomal function, enabling genetic selection workflows that rely on the neo cassette. It is commonly used alongside vectors or genomes encoding neomycin/kanamycin resistance to support the establishment and maintenance of engineered cell populations.