Gihon Spring or Fountain of the Virgin, also known as Saint Mary's Pool, is a spring in the Kidron Valley. It was the main source of water for the Pool of Siloam in Jebus and the later City of David, the original site of Jerusalem.

The term Pool of Siloam refers to a number of rock-cut pools on the southern slope of the Wadi Hilweh, located outside the walls of the Old City of Jerusalem to the southeast. The pools were fed by the waters of the Gihon Spring, carried there by the Siloam Tunnel.