Gallstone ileus of the colon is an exceedingly rare cause of large-bowel obstruction. It is usually the result of fistula formation between the gallbladder and large bowel facilitating entry of the stone into gastrointestinal tract. Contrast enhanced abdominal computed tomography is an important diagnostic aid. Surgical management is the treatment of choice to prevent the disastrous complications of large-bowel obstruction. We describe the case of a 92-year-old man who presented with symptoms and signs of large-bowel obstruction. Radiological investigation showed a large gallstone impacted in the sigmoid colon. Open enterolithotomy was undertaken relieving the obstruction and the patient made a full recovery.