The article presents a rare clinical case of sigmoid-rectal intussusception caused by a giant villous adenoma of the rectum. Clinical symptoms of the disease were manifested by mild pain in the lower abdomen, pain in the anus, partial intestinal obstruction with frequent loose stools. A tumor in the rectum was discovered during a routine digital rectal examination. Subsequent colonoscopic examination confirmed the presence of a tumor in the rectal ampulla, but did not detect intussusception. Computed tomography revealed the presence of sigmoid-rectal intussusception. Intraoperatively, it was possible to perform disinvagination with subsequent removal of the tumor and preservation of the rectum. After histological examination, the tumor was recognized as a giant villous adenoma. The postoperative period proceeded without complications, the patient was discharged in satisfactory condition with a functioning sigmoid stoma. Observation and examination over the next three months did not reveal further spread of the tumor process. The patient refused to have her stoma removed.