1-class oceanographic research ship (第一海洋型海洋観測船,, Daiichi Kaiyō-gata Kaiyō-kansokusen) was a class of oceanographic research ship/weather ship of the Imperial Japanese Navy (IJN), serving during World War II.

The IJN official designation was 200-ton oceanographic research ship (二〇〇瓲海洋観測船,, 200-ton Kaiyō-kansokusen).

In 1938, the IJN wanted to investigate the weather and ocean currents in a potential future battlefield.

The IJN made Hokkaido Fisheries Research Institute San'yō Maru a sample for the Kaiyō No.

All ships were deployed in the Hydrographic Department, and they were directly controlled by the Naval Ministry.