| State: | MS |
| Type: | MS |
| Route: | 15 |
| Maint: | MDOT |
| Map Custom: | yes |
| Length Mi: | 323.949 |
| Length Round: | 3 |
| Length Ref: | [1] |
| Established: | 1932 |
| Section1: | Southern segment |
| Section2: | Northern segment |
| Direction A: | South |
| Terminus A1: | in D'Iberville |
| Direction B: | North |
| Terminus B1: | near Wiggins |
| Direction A2: | South |
| Terminus A2: | near Beaumont |
| Junction2: | |
| Direction B2: | North |
| Terminus B2: | near Walnut |
| Counties: | Harrison, Stone, Perry, Jones, Jasper, Newton, Neshoba, Winston, Choctaw, Webster, Oktibbeha, Chickasaw, Pontotoc, Union, Tippah |
| Previous Type: | MS |
| Previous Route: | 14 |
| Next Type: | MS |
| Next Route: | 16 |
Mississippi Highway 15 (MS 15) is a state highway in Mississippi. At almost 324miles, 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).
Prior to 1966, MS 15 was one continuous route through the entire state of Mississippi.[2] The route formerly continued past I-10 and ran concurrent with I-110 to terminate at US 90.