Most colonic lipomas are asymptomatic and need no treatment, whereas lesions larger than 2 cm can cause acute abdominal pain, changes in bowel habits, gastrointestinal bleeding, intussusception or bowel obstruction. Autoamputation of polypoid lesions in the gastrointestinal tract is indeed a rare phenomenon, and its precise mechanism remains unknown. It presumably occurs due to ischemic necrosis of the polyp by peristalsis-induced torsion or tension. Here, we report a case of autoamputation of a giant colonic lipoma in a 48-year-old man. In our case, colonoscopic examination showed a huge autoamputated mass in the rectum and a remnant long stalk in the transverse colon. The autoamputated mass in the rectum was completely removed after fragmentation using an electrosurgical snare, and the remnant long stalk located in the transverse colon was also resected safely by endoscopic snare polypectomy. To our knowledge, these endoscopic treatments for removal of an autoamputated mass and a remnant long stalk of colonic lipoma have not been reported previously.