The Coventry-class frigates were 28-gun sixth rate frigates of the Royal Navy, principally in service during the Seven Years' War and the American Revolutionary War. They were designed in 1756 by Britain's Surveyor of the Navy, Sir Thomas Slade, and were largely modeled on HMS Tartar, which was regarded as an exemplar among small frigates due to its speed and maneuverability. The 1750s were a period of considerable experimentation in ship design, and Slade authorized individual builders to make "such alterations withinboard as may be judged necessary" in final construction.

In the rating system of the Royal Navy used to categorise sailing warships, a sixth-rate was the designation for small warships mounting between 20 and 28 carriage-mounted guns on a single deck, sometimes with smaller guns on the upper works and sometimes without. It thus encompassed ships with up to 30 guns in all. In the first half of the 18th century the main battery guns were 6-pounders, but by mid-century these were supplanted by 9-pounders. 28-gun sixth-rates were classed as frigates, those smaller as 'post ships', indicating that they were still commanded by a full ('post') captain, as opposed to sloops of 18 guns and less, which were under commanders.