St Catherine's Castle () is a small Device fort commissioned by Henry VIII. It is a two-storey building built to protect Fowey Harbour in Cornwall, United Kingdom. A twin battery of 64-pounder rifled muzzle-loading guns was added on a lower terrace in the 19th century. One emplacement was modified in WWII to mount a 4.7" naval gun inside a concrete shelter, but was later removed to restore the Victorian gun races.