This is one of six ratings (1st, 2nd, 3rd, 4th, 5th, 6th) in the rating system of the Royal Navy.

Sixth-rate was the designation used by the Royal Navy for small warships mounting between 22 and 28 nine-pounder guns on a single deck, sometimes with guns on the upper works and sometimes without. Sixth-rate ships crewed about 150 and measured between 450 and 550 tons. Usually sixth-rates were small frigates. Some larger ship-rigged , flush-decked vessels, were rated, which meant they were large enough to rate a Post-Captain in command, instead of a Lieutenant or Commander.

In later years sixth-rate frigates were sometimes called "jackass frigates", as they were really not quite big enough for proper frigate duties.

For ships smaller than sixth-rate, see main article rating system of the Royal Navy.