State Road A1A (SR A1A) is a major north–south Florida State Road consisting of seven separate sections running a total of 338.752 miles (545.168 km) along the Atlantic Ocean, from Key West at the southern tip of Florida, to Fernandina Beach, just south of Georgia on Amelia Island.

It is also called the Indian River Lagoon Scenic Highway from State Road 510 at Wabasso Beach to U.S. Route 1 in Cocoa.

In 2024, the entirety of A1A from Key West to the Georgia state line was designated the Jimmy Buffett Memorial Highway.

About a year and a half later, in November 1946, the State Road Board resolved to renumber the route due to confusion with the parallel U.S. Highway 1.

For most of its length, SR A1A runs along Florida's East Coast Barrier Islands, separated from the mainland of the state by the Intracoastal Waterway.

Today, SR A1A serves as more a main coastal highway that connects beach towns for more than 375 miles (600 km) along Florida's east coast.

The road heads east past East Martello Tower and Key West International Airport, before curving north with an intersection with CR 5A (Flagler Avenue), followed by the northern terminus of the Key West section of SR A1A, U.S. Route 1 and State Road 5 (the Overseas Highway).

Running along the south shore of Key West, SR A1A is the southernmost numbered highway in the lower 48 states.

A ferry takes traffic to the northern section of SR A1A that continues along the coast to just south of Fort Clinch State Park on the estuary of the Saint Mary's River.

At that point SR A1A hooks back south to Fernandina Beach and then turns west, going inland 20 miles through Yulee and crossing I-95 and U.S. Highway 17.

It serves as a paralleling alternate route to Federal Highway (US 1), and is often erroneously signed as SR A1A despite its official county designation and maintenance.

The longest of the four county spurs, County Road A1A is 15.88-mile (25.56 km) that runs along the Florida East Coast Railroad main line from Jonathan Dickinson State Park in Hobe Sound to Stuart, where it suddenly changes course and runs east along the south coast of the St. Lucie River.

East of Indian River Village Shopping Center, the road turns southward and becomes Atlantic Avenue.

It runs northeast from SR A1A, but begins to straighten out between John Drive and a private driveway south of F Street.

Once the road leaves the park, it features an exceptionally long west-to-north turning ramp towards SR A1A, but ends at the intersection of SRs A1A and 312.

The necessity for changing this Highway Number was because of confusion which has been experienced by the traveling public where US 1 and SR 1 are common or intersect each other.