The Large Millimeter Telescope (LMT) (Spanish: Gran Telescopio Milimétrico, or GTM) was inaugurated in Mexico on 22 November 2006. It is the world's largest and most sensitive single-aperture telescope in its frequency range, built for observing radio waves in the wave lengths from approximately 0.85 to 4 mm. It has an active surface with a diameter of 50 metres and 2000 m² of collecting area.
Millimeter wavelength observations using the LMT will give astronomers a view of regions which are obscured by dust in the interstellar medium, thus increasing our knowledge about star formation. The telescope is also particularly fitted for observing solar system planetesimals and planets and extra-solar protoplanetary disks which are relatively cold and emit most of their radiation at millimeter wavelengths. There are also proposals for observing fluctuations in the cosmic microwave background as well as active galactic nuclei.