Area code 661 is a telephone area code in the North American Numbering Plan for the southern part of the San Joaquin Valley and for the far northern part of the Los Angeles metropolitan area. The numbering plan area comprises most of Kern County, most of northern Los Angeles County (specifically the Santa Clarita Valley, the Antelope Valley and the surrounding mountains), and small parts of Ventura County, Santa Barbara County, and Tulare County. It was created in an area code split of area code 805 on February 13, 1999.

Principal cities in the numbering plan area are Bakersfield, Palmdale, Santa Clarita, and Lancaster.

This area code encompasses Edwards Air Force Base where the sound barrier was first broken by Chuck Yeager. The speed of sound at sea level is 661 knots, hence the correlation.

• List of California area codes
• List of North American Numbering Plan area codes