design: This study aims to investigate the effects of different dietary interventions, including low-fat diet, high-fat diet, and xylo-oligosaccharide supplementation at low and high doses, on the composition of the gut microbiota in C57BL/6 mice. Fresh fecal samples were collected from adult male mice after the intervention period and genomic DNA was extracted from each sample. The bacterial 16S rRNA gene V3V4 hypervariable regions were amplified using PCR with region-specific primers. The resulting amplicons were purified, quantified, pooled in equimolar ratios, and used to construct paired-end sequencing libraries. Libraries were sequenced on an Illumina NovaSeq 6000 platform to generate paired-end 282 bp reads. This dataset can be used to characterize fecal microbiome composition and to assess the impact of dietary factors on microbial community structure in mice.