HMS Halcyon was a Halcyon-class minesweeper built for the Royal Navy in 1933. She was the lead vessel in the class. Her pennant number was J42. Halcyon was built by John Brown Shipbuilding & Engineering Company Ltd., at Clydebank, in Scotland. She was laid down on 27 March 1933 and launched on 20 December of the same year. She was commissioned on 18 April 1934. Halcyon was sold for scrapping at Milford Haven on 19 April 1950 after 16-years service with the Royal Navy.