The Large Helical Device (大型ヘリカル装置, Ōgata Herikaru Sōchi) (LHD) is a fusion research device in Toki, Gifu, Japan, belonging to the National Institute for Fusion Science. It is the second largest superconducting stellarator in the world, after the Wendelstein 7-X. The LHD employs a heliotron magnetic field originally developed in Japan.