Einstein@Home is a volunteer computing project that searches for signals from spinning neutron stars in data from gravitational-wave detectors, from large radio telescopes, and from a gamma-ray telescope. Neutron stars are detected by their pulsed radio and gamma-ray emission as radio and/or gamma-ray pulsars. They also might be observable as continuous gravitational wave sources if they are rapidly spinning and non-axisymmetrically deformed. The project was officially launched on 19 February 2005 as part of the American Physical Society's contribution to the World Year of Physics 2005 event. Einstein@Home searches data from the LIGO gravitational-wave detectors. The project conducts the most sensitive all-sky searches for continuous gravitational waves. While no such signal has yet been detected, the upper limits set by Einstein@Home analyses provide astrophysical constraints on the Galactic population of spinning neutron stars. Einstein@Home also searches radio telescope data from the Arecibo Observatory, and has in the past analyzed data from Parkes Observatory. On 12 August 2010, the first discovery by Einstein@Home of a previously undetected radio pulsar J2007+2722, found in data from the Arecibo Observatory, was published in Science. This was the first data-based discovery by a volunteer computing project. As of July 2022 Einstein@Home had discovered 55 radio pulsars. The project also analyses data from the Fermi Gamma-ray Space Telescope to discover gamma-ray pulsars. On 26 November 2013, the first Einstein@Home results of the Fermi data analysis was published: the discovery of four young gamma-ray pulsars in LAT data. As of July 2022, Einstein@Home has discovered 39 previously unknown gamma-ray pulsars in data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The Einstein@Home search makes use of novel and more efficient data-analysis methods and discovered pulsars missed in other analyses of the same data. The project runs on the Berkeley Open Infrastructure for Network Computing (BOINC) software platform and uses free software released under the GNU General Public License, version 2. Einstein@Home is hosted by the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, Hannover, Germany) and the University of Wisconsin–Milwaukee. The project is supported by the Max Planck Society (MPG), the American Physical Society (APS), and the US National Science Foundation (NSF). The Einstein@Home project director is Bruce Allen. Einstein@Home uses the power of volunteer computing in solving the computationally intensive problem of analyzing a large volume of data. Such an approach was pioneered by the SETI@home project, which is designed to