Background: Robotic surgery for rectal cancer is gaining popularity, but persuasive evidence on long-term oncological outcomes is lacking. This multicenter randomized controlled trial compared robotic and conventional laparoscopic surgery regarding surgical quality and long-term oncological outcomes among patients with middle and low rectal cancer. Methods: This superiority trial was undertaken at 11 hospitals in 8 Chinese provinces. Patients with middle (> 7–12 cm from anal verge) or low (0–7 cm from anal verge) rectal adenocarcinoma, cT1–T3 N0–1 or ycT1–T3 Nx after preoperative radio-/chemoradiotherapy, and no evidence of distant metastasis were enrolled and randomly assigned in a 1:1 ratio to receive robotic or conventional laparoscopic surgery. Secondary (short-term) end points (surgical quality, pathological radicality, and postoperative recovery) were compared using modified intention-to-treat (mITT) analysis. Three-year locoregional recurrence rate as the primary endpoint is expected by the end of 2023. This trial was registered with ClinicalTrials.gov (NCT02817126). Results: Between July 2016 and December 2020, 1240 patients were enrolled; 1180 were included in the mITT analysis (591 in robotic and 589 in laparoscopic group). There were significantly more sphincter-preserving surgeries (low anterior resections) performed in the robotic group (83.1% vs. 76.9%, p = 0.008). With more macroscopic complete resections (95.4% vs. 91.9%, p = 0.012), robotic surgery had better integrity of the mesorectal fascia, and had lower circumferential resection margin positivity rate (4.0% vs. 7.1%, difference = -3.1%, 95% confidence interval = -6.0% to -0.5%, p = 0.023) and more lymph nodes harvested (median, 15.0 vs. 14.0, p = 0.004). Robotic surgery also reduced the open conversion rate (1.7% vs. 3.9%, p = 0.021), estimated blood loss (median, 40.0 ml vs. 50.0 ml, p < 0.001), intraoperative complication rate (5.4% vs. 8.7%, p = 0.029), and 30-day postoperative complication rate (Clavien-Dindo grade II or higher, 16.1% vs. 22.9%, p = 0.003), leading to better postoperative recovery and shorter postoperative hospital stay (median, 7.0 days vs. 8.0 days, p < 0.001). The 30-day postoperative mortality was similar between the two groups (0.2% vs. 0.2%, p > 0.999). Conclusions: Robotic surgery for middle and low rectal cancer significantly reduced surgical injury, improved oncological radicality, and promoted postoperative recovery compared with conventional laparoscopic surgery. Clinical trial information: NCT02817126.