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<i>Lactobacillus iners</i> is often associated with vaginal dysbiosis and bacterial vaginosis (BV), which are risk factors for adverse gynecological and obstetric outcomes. To discover natural inhibitors of <i>L. iners</i>, cell-free culture supernatants (CFSs) from 77 vaginal human <i>Lactobacillus</i> strains and 1 human intestinal strain were screened for inhibitory activity. Three active strains were identified, and <i>Lactobacillus paragasseri</i> K7 (K7), a human intestinal strain, produced the most potent <i>L. iners</i>-inhibitory activity. The active material was purified from the K7 CFS and yielded three active peptides, identified as components of two different class IIb, two-peptide bacteriocins, gassericin K7A (GasK7A) and gassericin K7B (GasK7B). The peptides corresponded to the GasK7A α peptide and the GasK7B α and β peptides. While all three peptides exhibited individual activity against <i>L. iners</i>, GasK7B α was the most potent, with an MIC of 23 ng/ml (4 nM). When combined in equal amounts, the GasK7B α and β peptides showed synergistic inhibition, with an MIC of 2 ng/ml (each peptide at 0.4 nM). Among the four major vaginal <i>Lactobacillus</i> species, the K7 bacteriocins selectively inhibited <i>L. iners</i> All 21 strains of <i>L. iners</i> tested (100%) were inhibited by the K7 bacteriocins, whereas <20% of the vaginal <i>Lactobacillus crispatus</i>, <i>L. jensenii</i>, and <i>L. gasseri</i> strains were inhibited. The combination of the BV treatment metronidazole and K7 bacteriocins completely killed both <i>L. iners</i> and <i>Gardnerella vaginalis</i> in a coculture experiment to mimic BV conditions. In contrast, this treatment did not inhibit <i>L. crispatus</i> cultures.<b>IMPORTANCE</b><i>Lactobacillus iners</i> is a prevalent species of the vaginal microbiome, but unlike other major vaginal <i>Lactobacillus</i> species, it is not considered protective against BV and can coexist with BV-associated bacteria. <i>L. iners</i> is generally the first <i>Lactobacillus</i> species to emerge following the treatment of BV with metronidazole, and mounting evidence suggests that it may contribute to the onset and maintenance of vaginal dysbiosis. The discovery of highly potent bacteriocins that selectively kill <i>L. iners</i> while sparing protective vaginal lactobacilli may provide novel pharmacological tools to better understand the roles of this enigmatic bacterium in vaginal ecology and potentially lead to new and improved therapies for dysbiosis-related conditions such as BV.