The Northern State Parkway (also known as The Northern State) is a 28.88-mile (46.48 km) long limited-access state parkway on Long Island in the U.S. state of New York. The western terminus is at the Queens–Nassau County line, where the parkway continues westward into New York City as the Grand Central Parkway. The eastern terminus is at New York State Route 347 (NY 347) and NY 454 in Hauppauge. The parkway is designated New York State Route 908G, an unsigned reference route. As its name implies, the parkway services communities along the northern half of the island.

In western Nassau County the parkway sports six lanes, three eastbound and three westbound, narrowing to four lanes total in central Nassau at the Wantagh Parkway (exit 33) and through its twelve miles (19 km) or so in western Suffolk County, where it ends. It was constructed in stages throughout the 1930s and again post-World War II in the late 1940s/early 1950s until it reached its current terminus in Hauppauge in 1965. The Northern State Parkway is an eastern extension of the Grand Central Parkway. It was part of master planner Robert Moses' extensive road-building campaign and was built as a sister road to the Southern State Parkway. In recent years its design has quickly become dated due to an increase in commuter traffic using the roadway, and numerous improvements have been made (including the widening from four to six lanes in Central Nassau west to the Nassau-Queens line where it becomes the Grand Central) or are still on paper.

Like its siblings in the State Parkway system on Long Island, the Hudson Valley, and in New York City, commercial truck traffic is banned from the parkway due to low overpasses. The Long Island Expressway (designated Interstate 495, abbreviated LIE) was built later on by Moses to handle truck traffic traveling between New York City and Long Island's famed East End. The LIE runs directly alongside the Northern State in some parts of Nassau County.

The Northern State Parkway begins at the Queens–Nassau county line in front of the Towers Country Club in Little Neck. After crossing the county line, the Northern State proceeds east through Lake Success as a six lane parkway, passing the northern end of the campus of Long Island Jewish Medical Center. A short distance east of the medical center, the parkway crosses under Lakeville Road and enters exit 25, which connects to Lakeville Road via Marcus Avenue. The parkway proceeds northeast through Lake Success, entering exit 26 which serves New Hyde Park Road. At this junction, the parkway remains in close distance of the Long Island Expressway (I-495). The parkway winds northeast through North Hills, approaching the eastbound lanes of the Long Island Expressway, but entering exit 27, which connects to Shelter Rock Road (County Route 8; CR 8).

The Northern State and the Long Island Expressway begin paralleling each other in both directions, passing north of Searingtown. Just east of exit 36 on the expressway, the Northern State breaks away to the east for a short distance through Albertson, entering exit 28, which connects to Willis Avenue. The six-lane parkway continues eastward through Albertson, crossing under a railroad line and entering exit 29, which connects to Roslyn Road. The Northern State then enters Old Westbury, passing a large set of baseball fields before becoming a divided parkway into exit 29A, where it connects to the Long Island Expressway. Now paralleling Glen Cove Road, the Northern State proceeds south into exit 30, I.U. Willets Road. A short distance to the south, the parkway enters Wheatley Hills Golf Club and into the village of Carle Place.

Through Carle Place, the Northern State enters exit 31, which connects to NY 25, crossing under NY 25B (Hillside Avenue). Bending east, the parkway crosses over NY 25 (Jericho Turnpike), entering exit 31A, which serves the northern terminus of the Meadowbrook State Parkway in Westbury. After the interchange, the parkway proceeds northeast, passing under Carle Road in Westbury, entering The Hedges section, where exit 32, serving Post Road, interchanges. The Northern State then crosses through Birchwood Knolls and West Jericho as a six-lane parkway, where it enters exit 33, the northern terminus of the Wantagh State Parkway. After crossing under the southbound lane access ramp, the Northern State crosses under a flyover from the Wantagh northbound, then entering exit 34 in the town of Oyster Bay, which serves Brush Hollow Road.

Continuing east through Jericho Gardens, the Northern State Parkway proceeds northeast as a four-lane roadway, passing north of Cantiauge Park as it enters West Birchwood. In West Birchwood, the Northern State bends northeast, beginning a new parallel with the Long Island Expressway. Like at exit 27, approaching the expressway, the Northern State enters interchange 35, which serves the concurrency of NY 106 and NY 107 (North Broadway). After the cloverleaf interchange, the parkway enters East Birchwood on a parallel of the Long Island Expressway, which connects to the Northern State via exit 42. Like the previous parallel, the Northern State forks east away from the expressway, crossing over a one-track railroad line through Birchwood. A short distance after, the parkway enters exit 36, a cloverleaf interchange with South Oyster Bay Road (CR 9) before entering Woodbury.

In Woodbury, the Northern State Parkway continues east, crossing under Woodbury Road before entering a partial cloverleaf interchange with NY 135 (the Seaford–Oyster Bay Expressway). After NY 135, the parkway bends northeast, entering exit 37, which connects to Manetto Hill Road. A short distance after, the parkway enters another interchange with the Long Island Expressway (exit 37A) and an interchange with Sunnyside Boulevard (exit 38). Here, the route enters Trail View State Park before becoming a divided four-lane parkway through dense woods. The parkway makes a gradual bend to the east, then southeast, crossing the county line into Suffolk County just west of exit 39. Now in the town of Huntington, the Northern State enters exit 39, which serves Round Swamp Road.

After exit 39, the Northern State Parkway proceeds eastward as a four-lane freeway, crossing through West Hills County Park, where it winds through dense woods east and southeast through Huntington. Passing north of a cemetery, the parkway enters exit 40, which was formerly a cloverleaf interchange with NY 110 (Walt Whitman Road). After exit 40, the Northern State proceeds northeast, passing south of Whitman Park before bending east once again near Old Country Road. The four-lane parkway becomes divided once again, crossing northeast through Huntington into exit 41, a diamond interchange with Wolf Hill Road. The parkway soon enters the Caledonia section of town, bending eastward under Dix Hills Road as it enters the Arista section of town. The parkway crosses back into Caledonia, entering a partial cloverleaf interchange with Deer Park Road (NY 231 and CR 35). This interchange serves as the northern terminus of NY 231.

After Deer Park Road, the Northern State Parkway bends northeast once again, leaving the Caledonia area before bending southeast as a four-lane parkway. A short distance later, the route enters the Vanderbilt section of Huntington, paralleling north of CR 67 (Vanderbilt Parkway). In Vanderbilt, the parkway enters exit 43, a junction with CR 4 (Commack Road). Immediately after crossing over Commack Road, the large cloverleaf interchange that is Exits 44 and 45 comes in. Exit 44 serves the Sagtikos State Parkway and exit 45 serves the Sunken Meadow State Parkway, which share the same right-of-way. Now in the town of Smithtown, the Northern State enters the hamlet of Commack. Through Commack, the parkway becomes a divided four-lane roadway once again, entering exit 46 eastbound, which connects to New Highway via a service road.

After exit 46, the Northern State Parkway bends northeast, crossing through Mayfair and east of Hoyt Farm Park. The parkway soon crosses under New Highway in Commack, before entering a large interchange with NY 347 and NY 454 (Veterans Highway). This unnumbered interchange serves as the eastern terminus of the Northern State Parkway, whose northbound lanes merge into NY 347/NY 454 east.

Between exits 38 and 39, the northern terminus of Bethpage State Parkway and southern terminus of Caumsett State Parkway were proposed to have an unconventional interchange at exits 38A and 38B, respectively.[citation needed]

Three service areas used to exist in widened areas of the median along the Parkway. The first was east of Meadowbrook State Parkway; the second was west of County Route 4 (CR 4, named Commack Road) in Suffolk County; the third was at the former terminus of the Northern State Parkway and existing terminus of the Sagtikos State Parkway.[citation needed]

The final 2.5-mile (4.0 km) long extension of the parkway, constructed between Sagtikos State Parkway and Veterans Memorial Highway, opened in June 1965. The only evidence of the formerly shared termini of the Northern and Sagtikos State Parkways can be found in what is now the east-to-south ramp of exit 44, which is wider than the other ramps, as well as those for exit 45 to the Sunken Meadow State Parkway.[citation needed]

Beyond NY 454, there were plans to extend the Northern State Parkway further east through Caleb Smith State Park Preserve, then along the Nissequogue River. After crossing NY 111, it would have turned south across Long Island until entering Connetquot River State Park Preserve, where it would include additional park entrances, then turn west finally terminating at Heckscher State Parkway between CR 17 (Carleton Avenue) and NY 27.

The interchange with New Highway in Commack will become a full diamond when the NY 347 reconstruction project is complete.[citation needed]

The interchange with NY 110 was originally a split exit, signed as exit 40S for southbound NY 110 and exit 40N for the northbound direction. In 2011, reconstruction of the interchange began. The two split exits have been combined into a single exit 40, and the original overpass carrying the parkway over NY 110 is being replaced. The project is still ongoing at the present time.

Exit numbers sequentially follow those of the Grand Central Parkway.