Giant left atrium is a condition characterized by huge enlargement of the left atrium with a diameter exceeding 65mm. It is most commonly associated with long standing rheumatic mitral valve disease. We present a 45-year-old female patient with rheumatic mitral stenosis associated with giant left atrium occupied by an 11 × 10 × 5 cm thrombus weighing 500 gms. The patient underwent successful mitral valve replacement and thrombectomy through an inverted T-shaped biatrial incision.