The Holland Tunnel is a vehicular tunnel under the Hudson River. It connects the New York City neighborhood of SoHo in Lower Manhattan to the east with Jersey City in New Jersey to the west. An integral conduit within the New York metropolitan area, the Holland Tunnel is operated by the Port Authority of New York and New Jersey. The tunnel carries Interstate 78; the New Jersey side is also designated the eastern terminus of Route 139. The Holland Tunnel is one of three vehicular crossings between Manhattan and New Jersey, the two others being the Lincoln Tunnel and the George Washington Bridge.

Plans for a fixed vehicular crossing over the Hudson River were first devised in 1906. However, disagreements prolonged the planning process until 1919, when it was decided to build a tunnel under the river. Construction of the Holland Tunnel started in 1920, and it opened in 1927. At the time of its opening, the Holland Tunnel was the longest continuous underwater vehicular tunnel in the world.

The Holland Tunnel was originally known as the Hudson River Vehicular Tunnel or the Canal Street Tunnel. It was renamed the Holland Tunnel in memory of Clifford Milburn Holland, the chief engineer, following his sudden death in 1924 before the tunnel was opened. The Holland Tunnel was the world's first mechanically ventilated tunnel; the ventilation system was designed by Ole Singstad, who oversaw the tunnel's completion.