| State: | AL |
| Type: | US-Alt |
| Route: | 72 |
| Map: | US 72A (AL) map.svg |
| Length Mi: | 67.526 |
| Length Ref: | [1] |
| Length Round: | 3 |
| Direction A: | West |
| Direction B: | East |
| Terminus A: | at Muscle Shoals |
| Junction: |
|
| Terminus B: | in Huntsville |
| Counties: | Colbert, Lawrence, Morgan, Limestone, Madison |
| Spur Type: | US |
| Spur Of: | 72 |
| Previous Type: | SR |
| Previous Route: | 19 |
| Browse Route: | SR 20 |
| Next Type: | SR |
| Next Route: | 21 |
Alternate U.S. Route 72 (US 72 Alt.) exists in Alabama on the south side of the Tennessee River between Muscle Shoals and Decatur, while US 72 follows on the north side of the river between Florence and Athens. US 72 Alt. crosses the Tennessee River at Decatur, along with US 31, and follows the entire route of Interstate 565 (I-565). SR-20 was co-signed with US 72 Alt. from Muscle Shoals to Huntsville but has since been truncated to the junction of I-65 just east of Decatur.
Originally, US 72 Alt. turned off SR-20 on to SR-53 / Jordan Lane in Huntsville and followed it north 1miles to rejoin with US 72. With the completion of I-565 in the early 1990s, US 72 Alt. was routed along with I-565 to the termination of I-565 at US 72 at Chapman Mountain.
US 72 Alt. begins at an intersection with US 43/US 72 in Muscle Shoals. Here, this road continues west as part of US 72. East of there, it intersects SR 157 at an at-grade intersection, where a concurrency begins.
A couple miles east of there, the roads split. SR 157 heads straight towards Moulton. US 72 Alt. turns due east at the interchange, heading towards Town Creek and Decatur.
US 72 Alt. enters Decatur after passing through Trinity, carrying SR 20. It serves as the northern terminus for The Beltline (SR 67) and continues eastward towards the town center. After traveling by the Old State Bank and the Dancy Polk House in the downtown area, US 72 Alt. intersects US 31. It continues over the "Steamboat Bill" Hudson Memorial Bridge, after which it and SR 20 continue east towards I-65 and I-565, while US 31 continues north towards Athens and Calhoun Community College. The route is essentially unsigned east of US 31.
After the interchange at I-65, US 72 Alt. becomes concurrent with I-565. The two routes run together for the entire length of I-565, passing through Mooresville, Madison, and Huntsville passing through intersections such as the University Drive and the elevated stretch. East of Downtown Huntsville, the routes ascend Chapman Mountain, where they intersect US 72, which serves as the eastern terminus for both I-565 and US 72A.