The three Churchill class, sometimes known as the Repeat Valiant-class submarines were nuclear-powered fleet submarines which served with the Royal Navy from the 1970s until the early 1990s. The Churchill class was based on the older Valiant class, but featured many internal improvements.

The Valiant class were a class of nuclear-powered fleet submarines in service with the Royal Navy from the mid-1960s until 1994. They were the first fully British nuclear fleet submarine; the earlier HMS Dreadnought used an American nuclear reactor. There were only two boats in the class, the first, Valiant commissioned in 1966 three years after Dreadnought, and Warspite the following year. Both were built by Vickers at Barrow-in-Furness.