The Ro-100-class submarine (呂百型潜水艦, Ro-hyaku-gata Sensuikan) was a group of medium-sized coastal submarines built for the Imperial Japanese Navy (IJN) during World War II. The IJN official designation for this class was Ko type submarine (小型潜水艦, Ko-gata Sensuikan, "Small type Submarine") or Senshō type submarine (潜小型潜水艦, Sen-Shō-gata sensuikan, "Submarine-Small Type"). They are also known as Type KS submarine. The type name was shortened to Sensuikan Ko-gata (潜水艦小型, Submarine-Small Type).