The coevolution of mammalian hosts and their beneficial commensal microbes has led to development of symbiotic host-microbiota relationships(1). Epigenetic machinery permits mammalian cells to integrate environmental signals(2); however, how these pathways are fine-tuned by diverse cues from commensal bacteria is not well understood. Here we reveal a highly selective pathway through which microbiota-derived inositol phosphate regulates histone deacetylase 3 (HDAC3) activity in the intestine. Despite the abundant presence of HDAC inhibitors such as butyrate in the intestine, we found that HDAC3 activity was sharply increased in intestinal epithelial cells of microbiota-replete mice compared with germ-free mice. This divergence was reconciled by the finding that commensal bacteria, includingEscherichia coli, stimulated HDAC activity through metabolism of phytate and production of inositol-1,4,5-trisphosphate (InsP(3)). Both intestinal exposure to InsP(3)and phytate ingestion promoted recovery following intestinal damage. Of note, InsP(3)also induced growth of intestinal organoids derived from human tissue, stimulated HDAC3-dependent proliferation and countered butyrate inhibition of colonic growth. Collectively, these results show that InsP(3)is a microbiota-derived metabolite that activates a mammalian histone deacetylase to promote epithelial repair. Thus, HDAC3 represents a convergent epigenetic sensor of distinct metabolites that calibrates host responses to diverse microbial signals. Phytate metabolism and production of inositol trisphosphate by commensal bacteria activates epithelial histone deacetylase 3 and promotes intestinal repair.