METAR is a format for reporting weather information.

METAR means "aviation routine weather report" and is predominantly used by pilots in fullfilment of a part of a pre-flight weather briefing. It is also used by meteorologists, who use aggregated METAR information to help forecast the weather.

METAR reports usually come from airports. Typically, reports are generated once an hour; however, if conditions change significantly, they may be updated in special reports called SPECI's. The format was introduced 1 January 1968 internationally and has been modified several times since. However, the United States and Canada did not adopt the format until 1 July 1996.

The word METAR is from the French, "message d'observation météorologique régulière pour l'aviation," and is thought to have originated as a contraction from MÉTéorologique ("Weather") Aviation Régulière ("Routine"). The FAA may consider it to be erroneous to abbreviate METAR as METeorological Aerodrome Report. The FAA and NOAA specifically define a METAR as an "aviation routine weather report," an approximate translation of the French.

A typical METAR report contains data for the temperature, dew point, wind, precipitation, cloud cover, cloud heights, visibility, and barometric pressure. A METAR report may also contain information on precipitation amounts, lightning, and other information that would be of interest to pilots or meteorologists such as Colour States. In addition, a short period forecast called a TREND may be added at the end of the METAR covering likely changes in weather conditions in the two hours following the observation. These are in the same format as a TAF. The complement to METAR reports, reporting forecasted weather rather than current weather, are TAFs. METARs and TAFs are used in VOLMET broadcasts.