DESY (Deutsches Elektronen-Synchrotron) is a national research centre for fundamental science located primarily in Hamburg with a second site in Zeuthen, Germany. It develops, builds and operates particle accelerators including PETRA III and FLASH for research in particle and high-energy physics, photon science and astroparticle physics. DESY is publicly financed by the German federal government and the states of Hamburg and Brandenburg and is a member of the Helmholtz Association.