Area code 251 is a telephone area code in the North American Numbering Plan (NANP) for southwestern Alabama, serving Mobile, Baldwin, and Washington counties and parts of six other counties.^[1] It was created on June 18, 2001, as a split from area code 334.^[2] In order to allow people time to reprogram electronics such as computers, cell phones, pagers and fax machines, use of the 334 area code continued in the 251 areas through January 7, 2002.^[3]

Prior to October 2021, area code 251 had telephone numbers assigned for the central office code 988. In 2020, 988 was designated nationwide as a dialing code for the National Suicide Prevention Lifeline, which created a conflict for exchanges that permit seven-digit dialing. This area code was therefore scheduled to transition to ten-digit dialing by October 24, 2021.^[4]