The Cyrus-class sixth rates of the Royal Navy were a series of sixteen-flush decked sloops of war built to an 1812 design by Sir William Rule, the Surveyor of the Navy.

The vessels of the class served at the end of the Napoleonic War.

They were built on the lines of HMS Hermes, which was based in turn on the French ship Bonne Citoyenne.

The Cyrus class was intended to be the counter to the new Frolic-class ship-rigged sloops that were under construction for the United States Navy.

[1] With the re-organisation of the rating system which took place in the Royal Navy effective from 1 January 1817, the Cyrus-class flush-decked ships were re-classified as 20-gun sloops.