Long Beach Island (colloquially known as LBI, The LBI Region, or simply The Island) is a barrier island and summer colony along the Atlantic Ocean coast of Ocean County, New Jersey, United States, on the Jersey Shore. Aligned north to south, the northern portion generally has more expensive low-density housing, whereas the southern portion possesses higher-density housing and considerable commercial development. Long Beach Island is 1–2 miles away from Mainland New Jersey. The primary industries include tourism, fishing, and real estate. The only access point to the island by land is a single causeway. The island is the southernmost point of the New York Metropolitan Area.

The island is home to about 10,000 people on a year-round basis. The population is distributed among six separate municipalities, the largest of which is Long Beach Township. However, the island's population swells significantly during the summer months and reaches about 100,000 people, including part-time residents and tourists, who are often referred to as "shoobies". The island's close-knit communities are largely affluent and contain vacation homes for wealthy individuals who reside elsewhere, primarily New Jersey as well as New York, Pennsylvania, and Connecticut.

The island and its properties and economy are expected to be severely affected by sea level rise. By 2013, sea level had increased by six inches and is expected to rise at least another six inches by 2030. Most projections suggest over a meter of sea level rise by 2100 and would require significant climate change adaptation to survive, making both property protection and an engineered retreat economically unattractive.

Long Beach Island is located 24 miles (39 km) north of Atlantic City 61 miles (98 km) east-southeast of Philadelphia and 101 miles (163 km) south of New York City. LBI is approximately 18 miles (29 km) in length, which includes three miles (4.8 km) of marsh protected as part of Edwin B. Forsythe National Wildlife Refuge located on the southern tip. The island is about a half-mile wide (800 m) at its widest point in Ship Bottom, and spans one-fifth of a mile (320 m) at its narrowest point in Harvey Cedars.

Long Beach Island is bisected by State Route 72, formerly "South 40", which connects the mainland to the island at Ship Bottom. It is the sole access point for road vehicles to the mainland over Manahawkin Bay. This results in the division of the island into a northern portion and a southern portion. From the bridge northward, the island includes the communities of Surf City, North Beach (a section of Long Beach Township), Harvey Cedars, Loveladies (a section of Long Beach Township), High Bar Harbor (the northernmost section of Long Beach Township), and Barnegat Light. From the bridge southward, the island includes the communities of Ship Bottom, North Beach Haven (a census-designated place in Long Beach Township that includes Brant Beach and Beach Haven Gardens), Beach Haven, and the Holgate section of Long Beach Township at the southernmost tip of the island.

The Lenape people were the original inhabitants of Long Beach Island, utilizing the island primarily as a summer retreat for fishing and clamming due to its abundant natural resources in the early 1600s. It wasn't until the 1690s, when the island became continuously settled on, initially by hunters and Europeans. Barnegat Inlet, to the north of the island, was an important path for freight shipments and whaling from the 17th century through the 20th century. Due to the inlet's importance and its turbulent waters, a lighthouse tower was constructed in 1835 to guide shippers through the area. Still, it was inadequate to ships, constantly being mistaken for another passing ship because the light was fixed. Erosion problems destroyed the tower in 1857, two years before the current Barnegat Lighthouse was completed in 1859, flashing at each compass point every 10 seconds. It was constructed by the United States Army Corps of Engineers under the supervision of George Gordon Meade, famous for leading the Union forces to victory four years later during the Civil War at the Battle of Gettysburg. The United States Life-Saving Service built Station #17 in Barnegat Light (then known as Brownsville) around 1872, which continues today as a United States Coast Guard station.

A developing tourism sector prompted the Tuckerton Railroad (a short line running from Tuckerton to Whiting) to build a bridge across Barnegat bay that ran from Barnegat city to Beach Haven; the tracks were completed in 1886 and were leased to the Pennsylvania Railroad (PRR). The Jersey Shore shark attacks of 1916 included a fatal attack in Beach Haven, killing University of Pennsylvania student Charles Vansant in July 1916, which partly inspired the book Jaws. A severe winter storm in 1920 destroyed most of the beaches along the island, several hotels, and reopening the new inlet in Holgate. A storm in 1923 further diminished the tourism sector, resulting in the discontinuation of train service to Barnegat City between 1923 and 1926. In 1935, the railroad bridge to the mainland washed out, leaving the entire island without rail service.

Several storms throughout the island's history have resulted in the island being split in two, with the division occurring at the island's narrowest point in Harvey Cedars. The most famous of such storms was the Ash Wednesday Storm of 1962, which split Long Beach Island into numerous pieces and nearly destroyed the island in its entirety. The storm caused the destroyer USS Monssen to run aground in Beach Haven Inlet, Long Beach Township. The existing Route 72 Causeway was erected in the late 1950s, which replaced a low-level two-lane automobile bridge which in itself had replaced the previously destroyed railroad bridge.