The Kaidai-type submarine was a type of first-class submarine operated by the Imperial Japanese Navy (IJN) before and during World War II. The type name was shortened to Kaigun-shiki Ōgata Sensuikan (海軍式大型潜水艦) Navy Large Type Submarine.

The 1st Naval Armaments Supplement Programme , otherwise known as the "Circle One" plan was the first of four expansion plans of the Imperial Japanese Navy between 1930 and the start of World War II.