Robert Gysae (January 14, 1911 – April 26, 1989) was a Korvettenkapitän with the Kriegsmarine during World War II. He commanded U-98 and U-177, sinking twenty-five ships on eight patrols, for a total of 146,815 gross register tons (GRT) tons of Allied shipping, to become the fifteenth highest scoring U-Boat ace of World War II.
Gysae joined the Reichsmarine in 1931 and served on torpedo boats before transferring to the U-bootwaffe ("U-boat force") in April 1940. In October 1940 he was appointed commander of the Type VIIC U-boat U-98, unusually without serving any time as either 1.WO (1. Wachoffizier, "1st Watch Officer") or Kommandantenschüler ("Commander-in-Training") on any other U-boats. After six patrols in the north Atlantic in command of U-98, in March 1942 he transferred to the Type IXD2 U-boat U-177 for another two patrols, this time operating off South Africa and Portuguese East Africa. He sank a total of 25 ships, including the armed merchant cruiser HMS Salopian. In January 1944 he became commander of 25th U-boat Flotilla, a training flotilla based at Gotenhafen. In April 1945, during the last month of the war, Gysae commanded the Marinepanzerjagd-Regiment 1, a naval anti-tank regiment. After the war he served in the Deutscher Minenräumdienst ("German Mine Sweeping Administration") for more than two years. In 1956 he joined the Bundesmarine, serving for four years as Navy attaché in the United States, and then three years as commander of Marinedivision Nordsee with the rank of Flottillenadmiral before retiring in 1970. He died in 1989 aged 78.