The National Optical Astronomy Observatory (NOAO) is the United States national observatory for ground based nighttime ultraviolet-optical-infrared (OUVIR) astronomy. The National Science Foundation (NSF) funds NOAO to provide forefront astronomical research facilities for US astronomers. However, professional astronomers from any country in the world may apply to use the telescopes operated by NOAO under the NSFs "open skies" policy. Astronomers submit proposals for peer review to gain access to the telescopes which are scheduled every night of the year for observations (with the exception of Christmas and New Years Eve). The combination of truly open access and the merit based science proposal process makes NOAO unique in the world. The NOAO headquarters are located in Tucson, Arizona and are co-located with the headquarters of the National Solar Observatory. The NOAO is operated by the Association of Universities for Research in Astronomy (AURA), under a cooperative agreement with the NSF. NOAO operates world class research telescopes in both the northern and southern hemispheres. These telescopes are located at Kitt Peak and Cerro Tololo in the US and Chile, respectively. Complemented with similar astronomical instruments, the two sites allow US astronomers to make observations over the entire sky. Instrumentation includes optical to near infrared wavelength (0.4 to 5 micrometres) cameras and spectrometers.