State Road A1A is a Florida State Road that runs mostly along the Atlantic Ocean, with sections from Key West at the southern tip of Florida, to Fernandina Beach, just south of Georgia on Amelia Island. It is the main road through most oceanfront towns. SR A1A is designated the A1A Scenic and Historic Coastal Highway, a National Scenic Byway. A portion of A1A that passes through Volusia County is designated the Ormond Scenic Loop and Trail, a Florida Scenic Highway. It is also called the Indian River Lagoon Scenic Highway from Wabasso Causeway to U.S. Route 1 in Cocoa.

In Key West it is also called South Roosevelt Boulevard. In Miami, it begins at MacArthur Causeway before becoming Collins Avenue at Fifth Street in Miami Beach (or, in small segments, Harding Avenue, Abbott Avenue, or Indian Creek Drive). In the town of Surfside, the northbound is Collins Avenue, and the southbound is Harding Avenue. In Bal Harbour it is called Bal Harbour Boulevard. In Golden Beach it is called Ocean Boulevard.

The designation is unique: other than SR A1A ALT (now SR 811, SR 707, SR 732, and an extension of SR 842), only two other Florida State Roads have begun with a letter: SR A19A (now a loop of SR 693-SR 699-SR 682 near St. Petersburg), and SR G1A (now SR 300) have existed.

The road was assigned the number SR 1 in the 1945 renumbering as the easternmost major north–south road. However, tourists and residents confused the road with the parallel U.S. Route 1, so the name was changed to SR A1A, which stands for "Atlantic 1 Alternate". The State Road Board changed the designation to SR A1A on November 25, 1946, about a year and a half after the renumbering. SR A1A is signed north–south.

SR A1A is heavily associated with Florida beach culture and is known for its lush tropical and subtropical scenery and ocean vistas. In many places, the highway directly fronts the Atlantic Ocean, and in other places, runs 1-5 blocks inland from the beachfront. For most of its length, A1A runs along Florida's East Coast Barrier Islands, separated from the mainland of the state by the Intracoastal Waterway. Because of the road's proximity to the ocean and its susceptibility to storm surges, sections of A1A are often closed or even damaged by hurricanes and tropical storms. North of Atlantic Beach, however, A1A turns inland for several blocks before resuming a northward course that ends at the St. Johns River. A ferry takes vehicular traffic to the northern section of A1A which continues along the coast to just south of a Florida State Park, Fort Clinch on the estuary of the Saint Marys River. At that point AIA hooks back south to Fernandina Beach and then turns West, going inland 20 miles through Yulee and crossing I-95, US 17 and finally terminating at US 1, 23, and 301 in Callahan. This section west of Fernandina Beach is also marked as SR 200, but SR AIA signs are displayed at every point of signage, though a designated direction is only above the SR 200 signs.

A1A also has been a backbone of Florida Spring Break, serving as "the strip" in both Fort Lauderdale, a popular spring break destination in the 1960s, 1970s, and 1980s, as well as Daytona Beach, which became a popular destination for college spring breakers in the 1980s through the present. In Miami Beach, A1A serves as Collins Avenue, one of the city's main north–south thoroughfares, and travels a similar route through exclusive Palm Beach, further to the north. In the Vero Beach area, it is known as The Robert C. Spillman Memorial Highway and it bridges Sebastian Inlet at the Sebastian Inlet Bridge. It then passes just to the west of Cape Canaveral and the Kennedy Space Center. Two miles of A1A were used as part of the legendary Daytona Beach Road Course. A1A also passes through St. Augustine, the oldest continuously-inhabited city in the mainland United States. It is known as Third Street in Jacksonville, Neptune, and Atlantic Beach.

SR A1A's southern terminus is at the southern end of Bertha Street, where SR A1A begins as a 2 lane, then 4 lane route along the Straits of Florida in Key West, known locally as South Roosevelt Boulevard. Running along the south shore of Key West, SR A1A is the southernmost numbered highway in the lower 48 states. The southern terminus is Bertha Street, where it heads east past East Martello Tower and Key West International Airport. SR A1A then curves to the north to U.S. Route 1/SR 5 (Overseas Highway), after intersecting with CR 5A (Flagler Avenue). SR A1A reappears at I-395 and US 1 in Miami.

Prior to the 1945 renumbering, the route that became SR 1 had the following numbers:

SR 1 was defined in the 1945 renumbering as:

Since then, the following changes have been made:

State Road 252 (also known as the Jungle Trail) was part of A1A in northeastern Indian River County, Florida. The narrow, seven-and-a-half mile long road is located between Old Winter Beach Road and the current A1A, along the western side of Orchid Island, and is unpaved. It is part of the Indian River Lagoon Scenic Highway system, and the southernmost road in the highway system.

The road started as a means to quickly transport citrus to packinghouses on the mainland, then in the 1930s and 1940s became more used by tourists. On August 1, 2003, it was added to the U.S. National Register of Historic Places.

County Road A1A is a county road in four counties in the U.S state of Florida. The route is discontinuous and functions as a spur of State Road A1A.

The longest of the four county spurs, Martin 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. After the terminus of SR 714, it approaces a bridge between Stuart and Sewall's Point and becomes SR A1A.

Volusia County Road A1A is a 7-mile (11 km) spur route of State Road A1A at Volusia County, Florida, United States. The route begins at U.S. Route 1 and State Road A1A at Downtown New Smyrna Beach as Lytel Avenue. Next, the route crosses the Intercoastal Waterway and Callalisa Creek before heading southbound. After the 2 bridges, the road becomes 3rd Avenue, the northern terminus of Saxon Drive as the first right after Callalisa Creek. East of Indian River Village Shopping Center, the road turns southward and becomes Atlantic Avenue. At the intersection of 27th Avenue, the road becomes 2 lanes wide. Less than a mile south of New Smyrna Beach, Saxon Drive ends. At Bethune Beach, the road slightly turns away from the Atlantic Ocean. The road became Turtle Mound Road at that point. After Bethune Beach, the road is midway between the Intercoastal Waterway and the Atlantic Ocean. At this point, a gate brings access to Canaveral National Seashore. It passes through the ghost town of Eldora. The road ends as a dead end at a beach.

St. Johns County Road A1A is a 3.40-mile (5.47 km) spur route of SR A1A in St. Augustine Beach that runs closer to the Atlantic Ocean than SR A1A. It runs northeast from SR A1A, but begins to straighten out between John Drive and a private driveway south of F Street. The closest thing resembling a major intersection is 16th Street. After passing by the St Johns County Ocean Pier, the road intersects Pope Road and leaves the city limits, where it enters Anastasia State Park, and makes a sharp curve to the west. Once the road leaves the park, it features an exceptionlly long west-to-north turning ramp towards SR A1A, but ends at the intersection of SRs A1A and 312.