Old Goa is a historical site and city situated on the southern banks of the River Mandovi, within the Tiswadi taluka (Ilhas) of North Goa district, in the Indian state of Goa.

The Mandovi or Mahadayi, formerly known as the Rio de Goa, is a river described as the lifeline of the Indian state of Goa. The Mandovi and the Zuari are the two principal rivers in the state of Goa. The Mandovi joins with the Zuari at a common creek at Cabo Aguada, forming the Mormugao harbour. Panaji, the state capital and Old Goa, the former capital of Goa, are both situated on the left bank of the Mandovi.