Ralf-Reimar Wolfram (31 March 1912 – 9 February 1945) was a Korvettenkapitän (lieutenant commander) during World War II. During his career he commanded two U-boats for a total of 118 days at sea spanning four patrols. During his third patrol he sank the SS Robert Gray, an American liberty ship. Robert Gray was a straggler from convoy HX 234 en route to Britain. For Wolfram's fourth patrol, he commanded GS U-864 during Operation Caesar. He was killed when U-864 was sunk by the British submarine HMS Venturer (P68). This was the only known instance of one submerged submarine sinking another submerged submarine. U-864 remains Wolfram's grave to this day.