John Catterall "Jack" Leach, DSO, MVO (1 September 1894 – 10 December 1941) was a British naval officer. He was the only captain of the battleship HMS Prince of Wales during her short period in service.
Very soon after the Prince of Wales entered active service in 1941, the ship fought under Leach's command in the Battle of the Denmark Strait, and suffered damage fighting the German battleship Bismarck. However, damage inflicted by the Prince of Wales caused the Bismarck to lose fuel, forcing the latter to attempt to return to a base in occupied France.
Despite a proposal to court-martial Leach for breaking off the action with the Bismarck after the Hood had sunk, he was awarded the Distinguished Service Order for his part. In the 1960 film Sink the Bismarck! Leach was played by actor Esmond Knight, who had been on the Prince of Wales' bridge with Leach during the Battle of the Denmark Strait and was partially blinded when the ship was hit by Bismarck's gunfire.
In late 1941, Prince of Wales formed part of Force Z sent to Singapore. Off the coast of Malaya, she was sunk by the Japanese. Captain Leach apparently abandoned Prince of Wales at the very last minute, but did not survive the vessel's sinking. His body was seen floating in the water a short time after the sinking.
His son was Henry Leach (1923–2011), who was First Sea Lord of the Royal Navy during the Falklands War.