State Route 17, or SR-17, is a 346.6-mile (557.8 km) long state route that runs the virtual length of the state. Between Mobile and Deer Park in Washington County, SR-17 is the unsigned partner route assigned to U.S. Highway 45, and from Hamilton to Florence, it serves as the signed partner route assigned to U.S. Highway 43.

The southern terminus of SR-17 and US-45 is at their junction with U.S. Highway 98 and unsigned State Route 42 in Mobile. US-45 and SR-17 assume a northwestwardly trajectory as they leave Mobile heading towards the Mississippi state line. Approximately five miles north of an interchange with Interstate 65 northwest of downtown Mobile, the routes quickly enter rural areas of Mobile County via a two-lane highway. Near the small community of Deer Park in southern Washington County, SR-17 diverts from US-45 and becomes a signed route.

After the split from US-45, SR-17 assumes a general northerly orientation as it passes through rural areas and small towns in western Alabama. The route passes through the Black Belt, historically one of the poorer areas of the state. After leaving Mobile, the route does not pass through any towns whose population exceeds 5,000 until it approaches Hamilton in Marion County. At Hamilton, SR-17 once again becomes an unsigned route upon the second junction it has with U.S. Highway 43; US-45 and SR-17 are the southern terminus of US-43 in Mobile.

Between Hamilton and Muscle Shoals, SR-17 is a signed route. At Muscle Shoals, US-43, SR-17 and SR-13 junction with U.S. Highway 72 and several other state routes. At this point, SR-17 once again becomes a signed route as it leads through Muscle Shoals and Florence as it heads towards its northern terminus at the Tennessee state line, where it becomes Tennessee State Route 13.

State Route 17 was designated in 1940 between Kennedy and York. In 1952, the route was extended south to Mobile; from York to Deer Park State Route 29 was renumbered as part of SR-17, and from Deer Park to Mobile the route ran together with U.S. Route 45. SR-17 was extended north to the Tennessee state line in 1956. To accomplish this, SR-17 replaced old State Route 19 up to Hamilton, was co-signed with U.S. Route 43 up to Florence, and replaced old State Route 34 the rest of the way to the Tennessee state line.