Miss. Code § 63-3-501
Except as otherwise provided in this section, no person shall operate a vehicle on the highways of the state at a speed greater than sixty-five (65) miles per hour.
The Mississippi Transportation Commission may, in its discretion, by order duly entered on its minutes, increase the speed restrictions on any portion of the Interstate Highway System provided such speed restrictions are not increased to more than seventy (70) miles per hour. The commission may likewise increase the speed limit to seventy (70) miles per hour on controlled access highways with four (4) or more lanes.
A governmental entity that operates and maintains a toll road as authorized under Section 65-43-1, or that contracts with some person or business to operate and maintain a toll road as authorized under Section 65-43-3, may establish the maximum speed for motor vehicles operated on any such toll road; however, the maximum speed so established may not exceed eighty (80) miles per hour.
Miss. Code § 63-3-501