The Grimsby class were a class of 13 sloops laid down between 1933 and 1940. Of these, eight were built in the United Kingdom for the Royal Navy, four in Australia for the Royal Australian Navy and one for the Royal Indian Navy. Main armament was initially two 4.7-inch (120 mm) guns for RN ships and three 4-inch (100 mm) for Australian ships, but armament varied considerably between ships, and was increased later.

In the 18th century and most of the 19th, a sloop-of-war in the Royal Navy was a warship with a single gun deck that carried up to eighteen guns. The rating system covered all vessels with 20 guns and above; thus, the term sloop-of-war encompassed all the unrated combat vessels, including the very small gun-brigs and cutters. In technical terms, even the more specialised bomb vessels and fireships were classed as sloops-of-war, and in practice these were employed in the sloop role when not carrying out their specialised functions.