The 18-pounder short gun was an intermediary calibre piece of artillery mounted on warships and merchantmen of the Age of sail.

It was a lighter version of the 18-pounder long gun, compromising power and range for weight.

In his discussion of the single-ship action in which the French frigate Piémontaise captured the East Indiaman Warren Hastings on 11 June 1805, the naval historian William James compared the 18-pounder medium guns on Warren Hastings with the 18-pounder long guns that the British Royal Navy used.

The medium 18-pounder was 6 ft (1.8 m) long, and weighed 26+3⁄4 long cwt (3,000 lb; 1,360 kg); the Royal Navy's long 18-pounder was 9 ft (2.7 m) and weighed 42+1⁄2 long cwt (4,760 lb; 2,160 kg).

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