A transatlantic tunnel is a theoretical tunnel which would span the Atlantic Ocean between North America and Europe and would carry mass transit of some type—trains are envisioned in most proposals. Using advanced technologies, speeds of 300 to 5,000 mph (500 to 8,000 km/h) are envisioned
Plans for such a tunnel have not progressed beyond the conceptual stage, and no one is actively pursuing such a project. Most conceptions of the tunnel have it between the United States and the United Kingdom, or more specifically, New York City and London. The main barriers to constructing such a tunnel are cost—as much as $12 trillion —and the limits of current materials science. Existing major tunnels, such as the Channel Tunnel and Seikan Tunnel, despite using less expensive technology than proposed for the Transatlantic tunnel, struggle financially. A Transatlantic Tunnel is 215 times longer than the longest current tunnel and would cost perhaps 3000 times as much.
In 2003, the Discovery Channel's show "Extreme Engineering" aired a program entitled "Transatlantic Tunnel" which discusses the proposed tunnel concept in detail.