GEO600 is a ground-based interferometric gravitational wave detector located near Hannover, Germany. It is designed and operated by scientists from the Max Planck Institute for Gravitational Physics and the Leibniz Universität Hannover, along with partners in the United Kingdom, and is funded by the Max Planck Society and the Science and Technology Facilities Council (STFC). GEO600 is part of a worldwide network of gravitational wave detectors. Two detectors have been constructed in the USA (LIGO), and one each in Italy (Virgo) and Japan (KAGRA). Scientists from GEO600 and LIGO collaborate within the LIGO Scientific Collaboration (LSC). GEO600 scientists together with the Laser Zentrum Hannover (LZH) built the lasers for Advanced LIGO.