The occurrence of ectopic lingual thyroid tissue was first reported over 100 years ago. We report an unusual presentation of ectopic thyroid tissue occurring in the submental area. A 27-year-old female presented to the Sultan Qaboos University Hospital in Muscat, Oman, in October 2011 with an 8 x 6 cm mass which caused difficulty in talking and a feeling of heaviness in the jaw. She was clinically and biochemically euthyroid upon presentation. The clinical diagnosis was confirmed by a technetium-99m thyroid scan, magnetic resonance imaging and fine needle aspiration. A single dose of 976 megabecquerels of radioactive iodine-131 resulted in hypothyroidism after three months and the complete disappearance of the swelling and associated symptoms. At a two-year follow-up, the patient was healthy and continuing lifelong replacement therapy with thyroxine.