The Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo (神岡宇宙素粒子研究施設, Kamioka Uchū Soryūshi Kenkyū Shisetsu, Japanese pronunciation: [kamioka ɯtɕɯː soɾʲɯꜜːɕi keŋkʲɯː ɕiseꜜtsɯ]) is a neutrino and gravitational waves laboratory located underground in the Mozumi mine of the Kamioka Mining and Smelting Co. near the Kamioka section of the city of Hida in Gifu Prefecture, Japan. A set of groundbreaking neutrino experiments have taken place at the observatory over the past two decades. All of the experiments have been very large and have contributed substantially to the advancement of particle physics, in particular to the study of neutrino astronomy and neutrino oscillation.