The National Astronomical Observatory of Japan (国立天文台 kokuritsu tenmondai) (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations - the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.
In 2004, after the Japan reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.