Interstate 59 (I-59) is an Interstate Highway located in the southeastern United States. It is a north–south route that spans 445.23 miles (716.53 km) from a junction with I-10 and I-12 at Slidell, Louisiana, to a junction with I-24 near Wildwood, Georgia.

The highway connects the metropolitan areas of New Orleans, Louisiana; Birmingham, Alabama; and Chattanooga, Tennessee, running closely parallel to the older U.S. Route 11 (US 11) corridor for the entire distance. Approximately one-third of the route, spanning 153 miles (246 km) from Meridian, Mississippi, to Birmingham, Alabama, overlaps that of the east–west I-20.

I-59 is a four-lane freeway along its entire route, other than a short stretch from Tuscaloosa, Alabama to the southern terminus of I-459 and in Birmingham, where it widens to six lanes or more. Aside from the metropolitan areas it passes through, the I-59 corridor is mainly rural in nature, especially in Georgia.

I-59 spans 11.48 miles (18.48 km) in Louisiana, the shortest distance in the four states through which it travels. The route begins at a partial cloverleaf interchange with I-10 (exit 267) and I-12 (exit 85) at the northeastern corner of Slidell, a city in St. Tammany Parish. From this interchange, connections are made to New Orleans and Hammond, as well as Bay St. Louis, Mississippi. Heading north, I-59 has two exits serving the town of Pearl River, where it begins a concurrency with US 11. Immediately afterward, the highway crosses the West Pearl River and passes through an interchange with Old US 11, a portion of the pre-Interstate alignment serving the Pearl River Wildlife Management Area. I-59 then travels through the Honey Island Swamp for six miles (9.7 km) before crossing the main branch of the Pearl River into Mississippi.

In Mississippi, I-59 continues to run parallel with US 11, traversing mainly rural areas but going through or bypassing the towns of Picayune, Poplarville, Hattiesburg, Moselle, Ellisville, Laurel, and Meridian.

For its length in Mississippi, I-59 either runs concurrently with, or runs close to, US 11. Between the towns of Pearl River and Picayune, US 11 travels concurrent with I-59. The highway also has concurrencies with US 98 in Hattiesburg; Mississippi Highway 42 (MS 42) just north of Hattiesburg; US 84 and MS 15 in Laurel; and US 80, US 11, and MS 19 in the Meridian area.^{[citation needed]}

A notoriously sharp S-curve, at milepost 96 in Laurel, was the subject of a large reconstruction project that began in 2006. Those sharp curves were the legacy of an overpass over the Southern Railway on a town bypass with design dating from before the Interstate Highways, and they featured a 40-mile-per-hour (64 km/h) speed limit, one of the lowest anywhere on the Interstate Highway System. This work was completed in 2009.

Just west of Meridian, I-20 joins I-59 and these two highways continue together for 153 miles (246 km), across the border with Alabama to and through Birmingham. The exit numbers are given as those of I-59.^{[citation needed]}