The Cross-Harbour Tunnel, or "XHT" for short, is the first tunnel in Hong Kong that was built under water. It connects Hong Kong Island and Kowloon at respectively Kellett Island (a former island now connected to Hong Kong Island by reclamation) and a reclaimed site at Hung Hom Bay.
Opened in 1972, the Cross Harbour Tunnel provides a road link between Kowloon and Hong Kong Island, making it possible to drive directly to and from the island. Prior to the tunnel's opening, cross-harbour vehicular traffic depended solely upon ferries. With the tunnel linking the main financial districts on both sides of Victoria Harbour, it became the busiest route in Hong Kong, with (as of March 2005) 121,700 vehicles using it daily. It was administered by The Cross-Harbour Tunnel Company Ltd until August 1999, when the operation franchise agreement expired and the government assumed control.