The Amethyst incident, also known as the Yangtze incident, was an historic event that occurred on the Yangtze River for three months in the summer of 1949, during the late phase of the Chinese Civil War. The incident involved the Communist People's Liberation Army (PLA), who were in the middle of a river-crossing offensive to overthrow the Nationalist Government, and four British Royal Navy ships HMS Amethyst, HMS Black Swan, HMS Consort and HMS London. The British warships, whose right of passage along the Yangtze had been unchallenged previously since the late Qing dynasty, came under bombardment by PLA artillery and were forced to withdraw permanently from Chinese territorial waters.

Commander John Simon Kerans was an officer in the Royal Navy and later a Conservative Party politician. He is also the author of the 1964 book The World's Greatest Sea Adventures, Publisher: Odhams Books Ltd.