The Seward Highway is a highway in the U.S. state of Alaska that extends 125 miles (201 km) from Seward to Anchorage. It was completed in 1951 and runs through the scenic Kenai Peninsula, Chugach National Forest, Turnagain Arm, and Kenai Mountains. The Seward Highway is numbered Alaska Route 9 (AK-9) for the first 37 miles (60 km) from Seward to the Sterling Highway, and AK-1 for the remaining distance to Anchorage. At the junction with the Sterling Highway, AK-1 turns west towards Sterling and Homer. About eight miles (13 km) of the Seward Highway leading into Anchorage is built to freeway standards. In Anchorage, the Seward Highway terminates at an intersection with 5th Avenue, which AK-1 is routed to, and which then leads to the Glenn Highway freeway.

The first portion of the Seward Highway was completed in 1923, and the highway was finished on October 9, 1951. The entire course of the highway was paved in 1952. In 1989, the highway was designated as a scenic byway by the U.S. Forest Service. The state of Alaska added the highway to its byway system in 1993, and in 2000 it was designated as an All-American Road, or National Scenic Byway.

The full length of the Seward Highway has been listed on the National Highway System (NHS), a network of roads important to the country's economy, defense, and mobility. The segment designated AK-9 between Seward and Tern Lake Junction is part of the STRAHNET subsystem, highways that are important to defense policy and which provide defense access, continuity and emergency capabilities for defense purposes. The remainder that follows AK-1 is also designated Interstate A-1 (A-1) and included in the NHS on that basis. The state's Interstate Highways are not required to comply with Interstate Highway standards, instead "shall be designed in accordance with such geometric and construction standards as are adequate for current and probable future traffic demands and the needs of the locality of the highway" under federal law. The highway is maintained by the Alaska Department of Transportation & Public Facilities (Alaska DOT&PF), and the A-1 designation is not signed along the highway. In 2010, 2,520 vehicles used the highway near the junction with Sterling Highway in a measure of the annual average daily traffic, the lowest tally along the highway. The highest traffic count as recorded by Alaska DOT&PF was 58,799 vehicles daily at the Dowling Road overpass in Anchorage. In 2012, Life Magazine included the Seward Highway in its list of Most Scenic Drives in the World.

The Seward Highway begins at an intersection with Railway Avenue, in Seward, Alaska, less than 100 yards (91 m) from the Gulf of Alaska. At this point, the Seward Highway is two lanes, with a parking lane on each side. The Seward Highway is designated as AK-9 at this point of the route. The highway continues through central Seward, passing several small businesses, houses, the Seward Museum, as well as several hotels and motels. The highway continues past the Seward Airport, before entering the unincorporated community of Bear Creek, Alaska. Just after entering Bear Creek, a series of tracks belonging to the Alaska Railroad comes alongside the roadway. These railroad tracks continue on with the Seward Highway until Crown Point, return near a junction with the Portage Glacier Highway, and remain until the highway becomes a freeway, in southern Anchorage. The Seward Highway proceeds through central Bear Creek, passing Bear Lake, until entering Chugach National Forest.

The Seward Highway enters the Chugach National Forest just five miles (8.0 km) after its start. The highway enters Chugach while it is still part of the Bear Creek community, so it gives the appearance of still being inside the CDP. After a mile or so (1.6 km), though, the area surrounding the highway begins to look more like a national forest. The Alaska Railroad weaves back and forth under the highway, which causes the highway to become a series of small bridges. For a few miles after the bridges, the Seward Highway is a four-lane road, but then merges into two. After passing through about 10 miles (16 km) of forest, the highway passes Primrose Spur Road, and enters Primrose, Alaska. For the next five or so miles (8 km), the route runs alongside Kenai Lake. Just before peeling off of Kenai Lake, the route passes though Crown Point, passes the single runway Lawling airport, and provides access to a large campground. The highway runs alongside the Trail River for about six miles (9.7 km), before passing the settlement of Moose Pass. The road continues, passing along Upper Trail Lake for a few miles, before peeling off and returning to the dense forest, and passing a large mountain range. After a few miles, the road passes the community of Tern Lake Junction, and intersects with Alaska Route 1 (AK-1), where Alaska Route 9 terminates, and the Seward Highway is designated to AK-1.

After that, for several miles, the roadway continues through large, Alaskan pine forests. After approximately 10 miles (16 km), the highway passes Summit Lake, and provides access to another large campground. The road then continues through a large mountain range on either side of the highway. After about eight miles (13 km), the route intersects the Hope Highway, which provides access to the city of Hope, Alaska, and the highway reenters forest. The roadway continues though forest for a brief period, and again enters the mountains. The route continues through the mountains for about 24 miles (39 km) more, before reaching the Turnagain Arm, and intersecting the Portage Glacier Highway. At this point, the Alaska railroad tracks again come alongside the route. The highway continues through the National Forest for approximately eight miles (13 km), passing the Turnagain arm to the west, and the Kenai Mountains to the east. It then exits the Chugach National Forest, having spent approximately 72 miles (116 km) inside the boundaries of Chugach National Forest.

After the highway exits the national forest, it continues for about five miles (8.0 km) through pine forest, before passing through the unincorporated community of Girdwood. After about a mile, the highway enters Chugach State Park. The road continues through forest for about 10 miles (16 km), before passing the small, unincorporated skiing village of Bird. The route reenters the park for about a mile, before entering the village of Indian, and then reentering the forest. The Seward Highway passes along the coast of the Gulf of Alaska for about 12 miles (19 km), with the Kenai Mountains running along the northern side. The highway then proceeds to enter the city limits of Anchorage. The highway intersects Old Seward Road, before becoming a four-lane freeway. The freeway's first exit is, in fact, for Old Seward Road. The freeway continues past several neighborhoods, a plant nursery, and Rabbit Creek Elementary School.

At an exit for De Armoun Road, the highway's frontage road begins. The freeway continues past dozens of neighborhoods, a few small businesses, and provides exits for a few small roads, including the Minnesota Drive Expressway. After the exit for Abbott Road, part of the frontage road terminates. The route then passes through a more commercial area of Anchorage, passing several warehouses. At the freeway's final exit, for Tudor Road, the rest of the frontage roads either begin or terminate. The freeway ends at the highways intersection with East 36th Avenue. About a half a mile (1 km) later, the highway splits into Ingra Street (northbound), and Gambell Street (southbound). The Seward Highway officially reaches its northern terminus at an intersection with 5th Avenue. AK-1 continues on for a short period as 5th Avenue, before becoming known as the Glenn Highway.

An 18-mile-long (29 km) stretch of the Seward Highway, traveling from Seward to Kenai Lake was completed in 1923. Another segment of the highway, running between Moose Pass and Hope, was completed in 1928. The Mile 18 bridge, nicknamed "The Missing Link", which would connect the Seward and Moose Pass portions, was not completed until 1946, which was a major cause of the delayed completion of the highway. The roadway was completed on October 19, 1951, connecting people Seward to the major city of Anchorage by road for the first time (the city was previously reached by sea, rail, or air). The entire length of the highway was paved in 1952.

The highway was designated a National Forest Scenic Byway by the U.S. Forest Service on September 8, 1989. Later, the State of Alaska added it to the State Scenic Byway system on January 29, 1993. The final designation was added on June 15, 2000, when the Seward Highway was named an All-American Road as part of the National Scenic Byway program by the U.S. Secretary of Transportation. The length of the highway traveling from the AK-1 and AK-9 intersection to the northern terminus is designated as Interstate A-3 by the National Highway System.

United States Bicycle Route 97 is a U.S. Bicycle Route located along Alaska Route 1. The bike route runs alongside the Seward Highway along the entire length of the highway. The bike route was created in 2011.

All exits are unnumbered.

The Old Seward Highway is an approximately 8 miles (13 km) long former routing of the Seward Highway. The road is located entirely within Anchorage, with a southern terminus near the Rabbit Creek neighborhood, and a northern terminus in the Midtown neighborhood. Both of the highways termini are points on the Seward Highway. The highway was created in 1951, along with most of the Seward Highway.

The Old Seward Highway begins at an intersection with the Seward Highway near the neighborhood of Rabbit Creek, in southern Anchorage. The route runs northward, concurrently named as Rabbit Creek Road. The route separates from Rabbit Creek Road, traveling northwest over the New Seward Highway and through the neighborhood of Oceanview. The route bends north, running parallel to the New Seward Highway. The roadway intersects Minnesota Drive/O'Malley Road, and continues northward through the Campbell/Taku neighborhood. The road proceeds north into Midtown, traveling through the neighborhood to the highway's northern terminus, an intersection with 34th Avenue. An exit ramp from the New Seward Highway serves as the beginning of the southbound lanes.

The Old Seward Highway was created in 1951, as part of the original routing of the Seward Highway. Beginning in 1976, the state of Alaska designated three projects to reroute a large portion of the Seward Highway. This rerouting would bypass the section of the highway that is now the Old Seward Highway. The final portion of the rerouting was completed in early June of 1998.

The Old Seward Highway has a short, 2.3 miles (3.7 km) long spur road that connects Potter Valley Road to the highway.