The Thames Tunnel is an underwater tunnel, built beneath the River Thames in London, connecting Rotherhithe and Wapping. It measures 35 feet (11 m) wide by 20 feet (6 m) high and is 1,300 feet (396 m) long, running at a depth of 75 feet (23 m) below the river surface measured at high tide. It was the first tunnel known to have been constructed successfully underneath a navigable river (although the Babylonians may have built the Euphrates Tunnel nearly 4,000 years earlier), and was built between 1825 and 1843 using Marc Isambard Brunel's and Thomas Cochrane's newly invented tunnelling shield technology, by Brunel and his son Isambard Kingdom Brunel.
The tunnel was originally designed for horse-drawn carriages, but was never used for that purpose. It now forms part of the London Overground railway network under ownership of Transport for London.