Background: Dextran sodium sulfate (DSS)-induced colitis serves as a preclinical model for studying gut dysbiosis and inflammation relevant to inflammatory bowel disease (IBD) and its long-term complication of colorectal cancer (CRC). Beetroot (Beta vulgaris L.) extract, rich in betalains, polyphenols, and nitrates, exhibits antioxidant and anti-inflammatory properties. This study investigated beetroot extract’s effects on gut microbiota composition and predicted functional pathways in DSS-induced colitis. Methods: Male BALB/c mice were divided into four groups: control (water), DSS-only, beetroot 250 mg/kg + DSS, and beetroot 500 mg/kg + DSS. Beetroot extract was administered orally for 14 days prior to and during DSS exposure. Gut microbial profiles were analyzed using 16S rRNA sequencing, while microbial diversity, community structure, and predicted metabolic functions were evaluated using Shannon, Chao1, PCoA, PERMANOVA, and PICRUSt2 analyses. Results: DSS administration significantly reduced body weight, microbial diversity, and Bacteroidota abundance, while increasing Proteobacteria and Desulfobacterota—a classic colitis-associated dysbiosis signature. Beetroot supplementation restored body weight and microbial balance in a dose-dependent manner, with the 500 mg/kg group showing near-complete normalization of the microbiota. Functional predictions revealed the upregulation of short-chain fatty acid (SCFA) biosynthesis, glutathione metabolism, and amino acid pathways, and suppression of lipopolysaccharide biosynthesis. Identified phytochemicals, including betanin, ferulic acid, and rutin, were associated with antioxidant and prebiotic activities that support microbial restoration. Conclusions: Beetroot extract mitigates DSS-induced gut dysbiosis and inflammation by enhancing microbial diversity, restoring SCFA-associated taxa, and promoting anti-inflammatory and antioxidant pathways. These findings highlight beetroot as a promising natural dietary intervention for colitis and microbiome-associated intestinal disorders. © 2026 by the authors.