Tower Subway - north entrance

The Tower Subway is a tunnel, dug in 1869, beneath the River Thames in central London, close to the Tower of London. Its alignment runs between Tower Hill on the north side of the river and Vine Lane (off Tooley Street) to the south. Its innovative method of construction provided the template for the construction in 1890 of the City & South London Railway, the first of London's "Tube" railways.

The tunnel is called a subway according to normal British usage, indicating a tunnel for pedestrians, and not to the American English usage, equivalent to underground rapid transit.

It is sometimes cited as the world's first underground tube railway, though it was not the first underground railway.