Mississippi Highway 15 (MS 15) is a state highway in Mississippi. At almost 324 miles (521 km), it is the longest highway in the Mississippi Highway System. MS 15 is divided into two sections due to a large gap between Stone County and Perry County. The southern section begins at Interstate 10 (I-10) and I-110 in Biloxi and ends at a junction with MS 26 near Wiggins, and the northern section begins at a junction with U.S. Route 98 (US 98) near Beaumont and ends as a continuation as SR 125 near Walnut. It serves a total of 15 counties (Harrison, Stone, Perry, Jones, Jasper, Newton, Neshoba, Winston, Choctaw, Webster, Oktibbeha, Chickasaw, Pontotoc, Union, and Tippah).