HMCS Cobalt was a Flower-class corvette of the Royal Canadian Navy which took part in convoy escort duties during the Second World War. She served primarily in the Battle of the Atlantic. She was named for Cobalt, Ontario.

Diffused lighting camouflage was a form of active camouflage using counter-illumination to enable a ship to match its background, the night sky, that was tested by the Royal Canadian Navy on corvettes during World War II. The principle was discovered by a Canadian professor, Edmund Godfrey Burr, in 1940. It attracted interest because it could help to hide ships from submarines in the Battle of the Atlantic, and the research project began early in 1941. The Royal Navy and the US Navy carried out further equipment development and trials between 1941 and 1943.