The intestinal microbiota plays an important role in colorectal cancer (CRC) progression. However, the effect of tissue-resident commensal bacteria on CRC immune surveillance remains poorly understood. Here, we analyzed the intratissue bacteria from CRC patient colon tissues. We found that the commensal bacteria belonging to the Lachnospiraceae family, including Ruminococcus gnavus (Rg), Blautia producta (Bp), and Dorea formicigenerans (Df), were enriched in normal tissues, while Fusobacterium nucleatum (Fn) and Peptostreptococcus anaerobius (Pa) were abundant in tumor tissues. Tissue-resident Rg and Bp reduced colon tumor growth and promoted the activation of CD8+ T cells in immunocompetent mice. Mechanistically, intratissue Rg and Bp degraded lyso-glycerophospholipids that inhibited CD8+ T cell activity and maintained the immune surveillance function of CD8+ T cells. Lyso-glycerophospholipids alone promoted tumor growth that was abrogated with Rg and Bp injection. Collectively, intratissue Lachnospiraceae family bacteria facilitate the immune surveillance function of CD8+ T cells and control colorectal cancer progression. Display omitted •Identification of tissue-resident microbiota in colon tissues of CRC patients•Ruminococcus gnavus (Rg) and Blautia producta (Bp) are enriched in normal colon tissues•Rg and Bp suppress CRC and promote activation of tumor-infiltrating CD8+ T cells•Rg and Bp degrade lyso-glycerophospholipids and restore CD8+ T cell function Zhang et al. identify the tissue-resident microbiota in colon tissues of CRC patients and show that the Lachnospiraceae family bacteria R. gnavus and B. producta are enriched in normal colon tissue and suppress CRC development in mice. These bacteria degrade lyso-glycerophospholipids and restore immune surveillance functions of CD8+ T cells.