Post ship was a designation used in the Royal Navy during the second half of the 18th century and the Napoleonic Wars to describe a ship of the sixth rate (see rating system of the Royal Navy) that was smaller than a frigate (in practice, carrying fewer than 28 guns), but by virtue of being a rated ship (with at least 20 guns), had to have as its captain a post captain rather than a lieutenant or commander. Thus ships with 20 to 26 guns were post ships, though this situation changed after 1817.Sea officers often referred to the post ships as frigates though technically the Admiralty scrupulously...