As of September 2009, 505 astronauts from 38 different countries had been active participants in manned space flights. This data is sourced from The Astronautic Records Commission of the Fédération Aéronautique Internationale (FAI), which is the organization that governs astronautics as well as other air sports.
The FAI sets the standards for determining who can be officially called an astronaut. According to the FAI, an astronaut is someone who has flown an altitude of at least 100 kilometers. In the United States, the National Aeronautics and Space Administration, or NASA, is the government's official space program in which U.S. astronauts function.