Objective: High-salt intake is associated with cardiovascular disease and hypertension. A substantial number of patients are sensitive to salt, but environmental factors influencing this phenomenon are poorly understood. The gut microbiome has not been considered in the context of salt and hypertension research to date. It is known to respond to fluctuations in lifestyle and diet, and is increasingly recognized as an important factor which influences host health and disease. Using next generation sequencing methods we aimed to determine the effect of a high-salt diet on gut microbiome composition. Methods and Results: Male C57BL6/J mice, 10 weeks of age, were individually housed and either subjected to a purified normal salt (0.5% sodium) or high-salt diet (4% sodium + 1% in drinking water) ad libitum for 14 days. Feces was collected on days 0 and 14 of the diets. DNA was extracted from feces, the V4 region of the 16S rRNA gene amplified with PCR. Samples were multiplexed and sequenced with MiSeq. Reads were quality controlled and operational taxonomic units (OTUs) were called by comparison to the Greengenes database. The high-salt diet created a distinct gut microbiome composition compared to the normal-salt diet (analysis of Jensen-Shannon divergence). Whereas normal diet’s gut microbiome is composed mostly of OTUs from the Bacteroidetes phylum (70% of reads), high-salt diet causes a shift in relative abundance to other phyla (increased Firmicutes:Bacteroidetes ratio). Moreover, the genus Allobaculum significantly spikes after high-salt feeding. Both phenomena have recently been implicated in obesity studies. Conclusion: An increase in dietary sodium chloride alters the gut microbiome composition. Our findings indicate new perspectives on how salt impacts the body.