HMS TB 81, originally named Swift, was a torpedo boat that served with the British Royal Navy.

She was built in 1884–1885 by the shipbuilder J Samuel White as a private venture, and was purchased for the Royal Navy in 1885, and was one of the largest torpedo boats of her time.

In 1884, the shipbuilder J. Samuel White began work on a new, torpedo boat, named Swift as a private venture (i.e. without an order from a customer).

[5] Tandem rudders were fitted, allowing Swift to be the most manoeuvrable British torpedo boat of the time, despite being the largest, having a turning circle of 225 feet (69 m).

[11][12] On 3 August 1901, during the 1901 Naval Manoeuvres, TB 81 was trying to intercept the prototype turbine-powered destroyer Viper when both ships ran aground on the Renonquet reef off Alderney in the Channel Islands.

[13] TB 81 served as a patrol boat during the First World War, operating out of Portsmouth and Portland, and being fitted with hydrophones and depth charges.