The Belt System is a series of connected limited-access highways that form a belt-like circle around the New York City boroughs of Brooklyn and Queens. The system comprises four officially separate parkways; however, three of the four are signed as the Belt Parkway. The three parkways that make up the signed Belt Parkway—the Shore Parkway, the Southern Parkway (not to be confused with the Southern State Parkway), and the Laurelton Parkway—are a combined 25.29 miles (40.70 km) in length.

The Shore Parkway, Southern Parkway, Laurelton Parkway, and Cross Island Parkway are collectively known as the "Belt System". The four components of the Belt System are designated as New York State Route 907C (NY 907C), NY 907D, NY 907B, and NY 907A, respectively, by the New York State Department of Transportation. All four numbers are reference route designations and are not signed. Excluding the Cross Island Parkway, the other three segments are now known collectively as the official "Belt Parkway". It is designated an east–west route, and its exit numbering system begins, in standard fashion, at the western terminus of the Shore Parkway, the westernmost parkway in the system. The numbering increases as the parkway proceeds eastward, and continues onto the Cross Island at the eastern terminus of the Belt Parkway. The north–south parkway retains the numbering scheme to its northern terminus.

The Belt Parkway begins at an interchange (exit 22) with the Gowanus Expressway in the Bay Ridge section of Brooklyn. Paralleling Third Avenue, the parkway turns west and crosses over the New York and Atlantic Railway, a freight line. Bypassing Bay Ridge, the Belt enters exit 1, which services 65th–67th Streets in Bay Ridge. Crossing south past Owls Head Park, the parkway turns southward and enters Shore Road Park, paralleling the shore of the Upper New York Bay. The eastbound lanes, the Belt Parkway passes several small parking areas that services as a viewing spot for the bay. Connections across the parkway to Bay Ridge are also present at these parking areas. Beginning the bend to the southeast, the parkway passes Andrew Lehman Field.

Just east of the field, the Belt Parkway comes within the shadows of the Verrazano-Narrows Bridge and enters exit 2, which serves as the southern terminus of Fourth Avenue. After crossing under the bridge, the westbound lanes enter exit 3 which connects to the Verrazano. Eastbound, the lanes from the bridge connecting to the Belt merge in, as the road enters Dyker Beach Park. During a short gap away from the shore, the Belt passes a parking area for Dyker Beach Park, entering exit 4, which services Bay 8th Street and 14th Avenue. Continuing along the park, the Belt begins to parallel Cropsey Avenue and passes another parking area before reaching exit 5, a junction with Bay Parkway. This marks the eastern end of Dyker Beach Park, and the route begins to parallel shoreline strip malls before reaching Calvert Vaux Park.

Now in the Gravesend section of Brooklyn, the Belt enters exit 6, which connects to Cropsey Avenue. Westbound, this junction is split into exit 6N and exit 6S, also serving Stillwell Avenue. The parkway bends eastward and crosses over the Coney Island Complex, a large railroad yard for the New York City Subway. Just before entering exit 7, the eastbound lanes cross just north of the Neptune Avenue subway station. Exit 7 eastbound services Ocean Parkway, which is met by exit 7B proceeding westbound. Westbound, exit 7A services Shell Road in Gravesend. Paralleling the namesake Neptune Boulevard, the parkway enters Sheepshead Bay and connections to Coney Island.

At exit 8, the Belt Parkway connects to Coney Island Avenue, approaching the namesake bay as it continues east. Paralleling Emmons Avenue through Sheepshead Bay, the parkway enters exit 9A eastbound, which connects to Knapp Street and exit 9B, which is a ramp to the eastern end of Emmons Avenue. Westbound, exit 9 services Knapp Street. Crossing south of Gerritsen Beach, the parkway passes south of the Plum Beach Channel and passes a small rest area on the eastbound lanes. Turning northeast through the Floyd Bennett Field area, the parkway bends north and passes a service area with gas services in the median. Just north of the service area, the Belt enters exit 11N–S, a cloverleaf interchange which connects to Flatbush Avenue and the Rockaways.

After exit 11N, the Belt Parkway continues east through Floyd Bennett Field, crossing over the Mill Basin Drawbridge into Brooklyn Beach and passes the entrance to the Jamaica Bay Riding Academy, the only business served directly on the parkway. Crossing over another bridge, the parkway enters the Canarsie section of Brooklyn. The parkway, now running northeast, parallels a bicycle path, reaching Canarsie Pier and exit 13, which serves as the southern end of Rockaway Parkway. Crossing over another bridge, the parkway enters exit 14, which connects to Pennsylvania Avenue in Starrett City. After crossing another waterway, the Belt passes a former landfill and enters exit 15, a diamond interchange with Erskine Street.

Now crossing over Jamaica Bay, the Belt Parkway continues northeast in the borough of Queens, entering exit 17N–S, Cross Bay Boulevard and Cohancy Street, which also connects to the Cross Bay Bridge and towards the Rockaways. Crossing into an interchange with NY 27, the parkway crosses over the A line and passes exit 18B, which connects to Aqueduct Racetrack in Ozone Park.

Now on the Southern Parkway section of the Belt, the Belt continues eastward into exit 19, which connects to NY 878 (the Nassau Expressway) and I-678, the Van Wyck Expressway. This interchange also serves as access to John F. Kennedy International Airport. Now with Conduit Boulevard serving as frontage roads for the parkway, passing exit 20, a junction with the JFK Expressway and the airport. Crossing under the Van Wyck, the Belt continues east through multiple underpasses and overpasses before reaching exit 21A, eastbound, which services 150th Street and Rockaway Boulevard. Crossing under Guy R. Brewer Boulevard, the Belt enters exit 21B, which connects to Farmers Boulevard and Guy R. Brewer Boulevard.

Exit 22 services Springfield Boulevard, where the Belt Parkway begins to parallel a Long Island Rail Road line through Laurelton. Wesbound, exit 23A services North Conduit Boulevard (NY 27) and 225th Street, while eastbound, exit 23B services NY 27 and the Sunrise Highway. At this junction, the parkway turns northeast and joins the Laurelton Parkway segment, which connects to exit 24A and Francis Lewis Boulevard on the westbound lanes. Exit 24B on the eastbound lanes connects to Merrick Boulevard, which is connected via exit 24A westbound. Just after crossing under 130th Street, the Belt enters exit 25A–B. At this interchange, the Laurelton Parkway segment ends, with exit 25A connecting to the eastern terminus of the Southern State Parkway and exit 25B servicing Elmont Road.

At this interchange, the Belt Parkway crosses under the Southern State and becomes the Cross Island Parkway, which continues north through Queens, connecting to I-495, the Grand Central Parkway and eventually I-678, the Whitestone Expressway.

The Belt Parkway was proposed by builder and highway advocate Robert Moses in 1930 to provide modern highway access to Manhattan and to connect to, and use similar design principles to, parkways already constructed on Long Island and Westchester County, New York. Construction began in 1934. The full loop was completed when the Brooklyn–Queens Expressway (also known as the "BQE") was finished in 1960.

Though some signage bears the name "Belt Parkway," the original plan never called for a highway of that name, rather a system of different named parkways called the "Belt System." The Belt System is made up of a series of interconnecting highways, none of which are actually named the Belt Parkway. Originally, the highways were the Gowanus Parkway from the Brooklyn–Battery Tunnel to the Shore Parkway; the entirety of the Shore, Southern, Laurelton, and Cross Island Parkways; the Whitestone Parkway from the Cross Island to the Grand Central Parkway; and the Grand Central from the Whitestone to the Triborough Bridge.

All the original parkways, except the Gowanus, were built on grassy rights-of-way with trees, in a more pleasant surrounding than most highways of their time. The Gowanus Parkway, in part replacing the demolished Fifth Avenue Line, was built as an elevated structure over Third and Hamilton Avenues in order to avoid the active docks and industrial areas including Sunset Park, Brooklyn.

Like most parkways in New York State, the parkways comprising the Belt System were closed to commercial traffic, including any vehicle with a non-passenger registration and all commercial trucking of any size. Originally even station wagons, which had "suburban" registrations, were excluded but they were later allowed, along with passenger-registered SUVs and vans.

The system was not completed as a parkway, and some portions of the original system were converted to expressways, which allows commercial traffic to use them. These expressway portions included the Gowanus Expressway, replacing Gowanus Parkway as a connector between Manhattan and the Verrazano-Narrows Bridge to Staten Island and New Jersey (now signed as part of I-278); Whitestone Expressway, which converted Whitestone Parkway into a truck route to connect the Van Wyck Expressway to the Bronx–Whitestone Bridge (now signed as part of I-678); and the Brooklyn–Queens Expressway, built as an expressway to connect the Gowanus Parkway/Expressway to the Triborough Bridge and Grand Central Parkway to complete the system (now signed as part of I-278).