Southwest Airlines Co. is a major U.S. airline, the world's largest low-cost carrier, headquartered in Dallas, Texas / USA.

The airline was established in 1967 by Herb Kelleher and adopted its current name (Southwest Airlines) in 1971. The airline has more than 52,000 employees as of July 2016 and operates more than 3,900 departures a day during peak travel season. As of 2014, it carried the most domestic passengers of any U.S. airline. As of July 2016, Southwest Airlines had scheduled services to 100 destinations in the United States and seven additional countries, with service to three airports in Cuba starting late in 2016.

Southwest Airlines has used only Boeing 737s, except for the period from 1979 to 1987 when it leased some Boeing 727s from Braniff International Airways. As of January 2016, Southwest is the largest operator of the Boeing 737 worldwide, with over 700 in service, each averaging six flights per day.