Three ships of the Royal Navy

Royal Navy

The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

 have borne the name HMS Alligator, after the marine reptile, the alligator

Alligator

An alligator is a crocodilian in the genus Alligator of the family Alligatoridae. There are two extant alligator species: the American alligator and the Chinese alligator ....

. A fourth ship was planned but later cancelled:
was a 14-gun sloop

Sloop-of-war

In the 18th and most of the 19th centuries, a sloop-of-war was a warship with a single gun deck that carried up to eighteen guns. As the rating system covered all vessels with 20 guns and above, this meant that the term sloop-of-war actually encompassed all the unrated combat vessels including the...

 launched in 1780 and captured by the French in 1782. was a 28-gun Sixth Rate launched in 1787 and sold in 1814. was a 28-gun sixth rate launched in 1821, on harbour service from 1846 and sold in 1865.

• HMS Alligator was to have been a wooden screw corvette
  Corvette
  A corvette is a small, maneuverable, lightly armed warship, originally smaller than a frigate and larger than a coastal patrol craft or fast attack craft , although many recent designs resemble frigates in size and role...
  
  . She was laid down in 1860, but cancelled in 1863.