Lanai (Hawaiian: Lānaʻi, Hawaiian: [laːˈnɐʔi, naːˈnɐʔi], /ləˈnaɪ, lɑːˈnɑːi/ lə-NY, lah-NAH-ee, also US: /lɑːˈnaɪ, ləˈnɑːi/ lah-NY, lə-NAH-ee,) is the sixth-largest of the Hawaiian Islands and the smallest publicly accessible inhabited island in the chain. It is colloquially known as the Pineapple Island because of its past as an island-wide pineapple plantation. The island's only settlement of note is the small town of Lanai City. The island is 98% owned by Larry Ellison, cofounder and chairman of Oracle Corporation; the remaining 2% is owned by the state of Hawaii or individual homeowners.

Lanai has a land area of 140.5 square miles (364 km), making it the 43rd largest island in the United States. It is separated from the island of Molokaʻi by the Kalohi Channel to the north, and from Maui by the Auʻau Channel to the east. The United States Census Bureau defines Lanai as Census Tract 316 of Maui County. Its total population rose to 3,367 as of the 2020 United States census, up from 3,193 as of the 2000 census and 3,131 as of the 2010 census. As visible via satellite imagery, many of the island's landmarks are accessible only by dirt roads that require a four-wheel drive vehicle due to the lack of paved roadways.

There is one school, Lanai High and Elementary School, serving the entire island from kindergarten through 12th grade. There is also one hospital, Lanai Community Hospital, with 24 beds, and a community health center providing primary care, dental, behavioral health and selected specialty services in Lanai City. There are no traffic lights on the island.

Lanai was under the control of nearby Maui before recorded history. Its first inhabitants may have arrived as late as the 15th century.

The Hawaiian-language name Lānaʻi is of uncertain origin, but the island has historically been called Lānaʻi o Kauluāʻau, which can be rendered in English as "day of the conquest of Kauluāʻau". This epithet refers to a legend about a Mauian prince who was banished to Lanai because of his wild pranks at his father's court in Lāhainā. The island was said to be haunted by Akua-ino, ghosts and goblins that Kauluāʻau chased away, bringing peace and order to the island and regaining his father's favor as a consequence.

The first people to migrate here, most likely from Maui and Molokaʻi, probably established fishing villages along the coast at first, and then spread into the interior, where they raised taro in the fertile volcanic soil. During most of this period, the Mōʻī of Maui had control over Lanai, but generally left its inhabitants alone. However, at some point, King Kamehameha I or Kalaniʻōpuʻu-a-Kaiamamao invaded and killed many of them. The population must have been mostly eradicated by 1792, because in that year Captain George Vancouver reported that he had ignored the island during his voyage because of its apparent lack of inhabitants or villages. Lanai is said to have been Kamehameha's favorite fishing spot among Hawaii's main eight islands.

The history of sugar cultivation in Hawaii begins in Lanai, when in 1802 a farmer from China, Wong Tse Chun, produced a small amount there. He used a crude stone mill that he had brought with him to crush the cane.

In 1854 a group of members of the Church of Jesus Christ of Latter-day Saints were granted a lease in the ahupuaʻa of Pālāwai. In 1862 Walter M. Gibson arrived on Lanai to reorganize the settlement. A year later he bought the ahupuaʻa of Pālāwai for $3000; he used money of the church but titled the land in his own name. When the members of the Church found this out they excommunicated him, but he was still able to retain ownership of the land. By the 1870s, Gibson, then the leader of the colony on the island, had acquired most of the island's land, which he used for ranching.

By 1890, the population of Lanai had been reduced to 200. In 1899, Gibson's daughter and son-in-law formed Maunalei Sugar Company, headquartered in Keomuku, on the windward (northeast) coast, downstream from Maunalei Valley. The company failed in 1901. However, between 1899 and 1901 nearly 800 laborers, mostly from Japan, had been contracted to work for the plantations. Many Native Hawaiians continued to live along the less arid windward coast, supporting themselves by ranching and fishing.

By 1907, approximately half of the island was owned by cattle rancher Charles Gay. Backed by sugar planter William G. Irwin, Gay worked to acquire the remaining land. While the Hawaiian Organic Act would have made it illegal for the territorial government to sell such a large portion of land to Gay, a land exchange deal circumvented that law. Gay transferred several acres of land of what is now downtown Honolulu in exchange for the rest of the land on Lanai. The transfer was completed on April 10, 1907 and Gay mortgaged the land the very same day to Irwin for $200,000. By 1909, Gay had defaulted on the mortgage and officially conveyed the land to Irwin for a rebuttable presumption of consideration of $1. From this conveyance comes the common myth that the land was bought for a mere $1, when the true cost of the land included the $200,000 mortgage.

In 1921, Charles Gay planted the first pineapple plant on Lanai. The population had decreased again - to 150 - most of whom were the descendants of the traditional families of the island. A year later, James Dole, the president of Hawaiian Pineapple Company (later renamed Dole Food Company), bought the island and developed a large portion of it into the world's largest pineapple plantation.

Upon Hawaii statehood in 1959, Lanai became part of the Maui County.

In 1985, Lanai passed into the control of David H. Murdock as a result of his purchase of Castle & Cooke, which was then the owner of Dole. High labor and land costs led to a decline in Hawaii pineapple production in the 1980s, and Dole phased out its pineapple operations on Lanai in 1992.

In June 2012, Larry Ellison, then CEO of Oracle Corporation, purchased Castle & Cooke's 98 percent share of the island for $300 million. The state and individual homeowners own the remaining 2 percent, which includes the harbor and the private homes where the 3,000 inhabitants live. Ellison stated his intention to invest as much as $500 million to improve the island's infrastructure and create an environmentally friendly agricultural industry. Ellison had spent an estimated $450 million to remodel his Four Seasons Resort Lanai, which reopened in April 2016. He would also remodel his other resort in 2020 and has explained plans for further green energy projects by buying out diesel-powered utility assets, though he has since ended this plan.

According to Hawaiian legends, man-eating spirits have occupied the island. For generations, Maui chiefs believed in these man-eating spirits. Differing legends say that either the prophet Lanikāula drove the spirits from the island or the unruly Maui prince Kauluāʻau accomplished that heroic feat. The more popular myth is that the mischievous Kauluāʻau pulled up every breadfruit tree (ʻulu) he could find on Maui. Finally his father, Kakaʻalaneo had to banish him to Lanai, expecting him not to survive in that hostile place. However, Kauluāʻau outwitted the spirits and drove them from the island. The chief looked across the channel from Maui and saw that his son's fire continued to burn nightly on the shore, and he sent a canoe to Lanai to bring the prince back, redeemed by his courage and cleverness. As a reward, Kakaʻalaneo gave Kauluāʻau control of the island and encouraged emigration from other islands. Kauluāʻau had, in the meantime, pulled up all the breadfruit trees on Lanai, accounting for the historic lack of them on that island.

The highest point in Lanai is Mount Lānaʻihale. It is an inactive volcano near the center of the island and to the east of Lanai City. The elevation of Mount Lānaʻihale is 3,366 ft (1,026 m).

Lanai was traditionally administered in 13 political subdivisions (Ahupuaʻa), grouped into two districts (mokuoloko): kona (Leeward) and koʻolau (Windward). The ahupuaʻa are listed below, in clockwise sequence, and with original area figures in acres, starting in the northwest of the island.

Nr.	Ahupuaa	Area acres	Area km	Population
1	Kaa	19468	78.78	207
2	Paomai	9078	36.74	147
3	Mahana	7973	32.27	1
4	Maunalei	3794	15.35	0
5	Kalulu	6078	24.60	1
6	Kaunolu	7860	31.81	3
7	Palawai	5897	23.86	1
8	Pawili	1930	7.81	0
9	Kaohai	9677	39.16	1
10	Kamao	2751	11.13	2
11	Kealia Aupuni	5897	23.86	2
12	Kealia Kapu	1829	7.40	1
13	Kamoku	8291	33.55	2804
	Lanai	90523	366.33	3170

Kamoku hosts the largest share of population, because the bigger part of Lanai City falls into it. Parts of Lanai City stretch to Kaa and Paomai. As of 2010, the remaining ahupuaʻa were virtually uninhabited. According to the census of 2020, Lanai City accounts for 99 percent of the island population (3332 of 3367). As a census-designated place, Lanai City is defined solely for statistical purposes, and not by administrative boundaries.

A volcanic collapse in Lanai 100,000 years ago generated a megatsunami that inundated land at elevations higher than 300 metres (980 ft).

Tourism on Lanai began to be prominent in more recent history as the pineapple and sugarcane industries were phased out in the islands. The number of visitors coming to the island is still relatively small, however, with around 59,000 arrivals forecast for 2016. Of all the publicly accessible Hawaiian islands, only Molokaʻi attracts fewer visitors.

As of 2016, the two resort hotels on Lanai were managed by Four Seasons Hotels; the Four Seasons Resort Lanai in Manele Bay at Hulupoe Beach. The Hotel Lanai in Lanai City was built in 1923 by James Dole of the Hawaiian Pineapple Company as a lodge to house the executives overseeing the island's pineapple production. It was the island's only hotel until 1990.

Lanai is also home to three golf courses, one at each Four Seasons resort and a third, free course.

• The Challenge at Manele borders the ocean and was designed by Jack Nicklaus. Bill Gates was married on the 12th hole tee-box at The Challenge at Manele.
• The Experience at Koele is located in the mountains of Lanai and was designed by noted Southern California golf course architect Ted Robinson Sr, with input from Greg Norman.
• The Cavendish is a public golf course designed by E.B. Cavendish in 1947. It is a nine-hole course surrounded by Norfolk pines.

Shipwreck Beach on the north shore of the island is so named because of the remains of a wrecked vessel aground a short distance offshore. This is popularly referred to as a WW II Liberty Ship, although it is YOG-42, one of several concrete barges built during the war.

In Lanai City, there are no traffic lights. Public transportation is supplied by the hotels. Most attractions outside of the hotels and town can be visited only via dirt roads that require an off-road vehicle, bicycle or walking.

Lanai is served by Lanai Airport, which offers air taxi and scheduled commercial operations to other Hawaiian islands.

• Danny Lockin, actor, dancer, born in Lanai in 1943. Best known for his role as Barnaby Tucker in the 1969 movie Hello, Dolly!, he played the same role in the Broadway play when it went on tour across the United States.

• 
  Housing in Lanai City
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  Keahiakawelo
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  Mountains on Lanai
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  Kaneapua Rock
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  Walls of Halulu Heiau at Kaunolu Village Site
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  View of the night sky from inside of Dole Park

• National Register of Historic Places listings in Lanai

• Lānaʻi Culture & Heritage Center
• "Chapter 6: Lānaʻi" (PDF). Hawaii's Comprehensive Wildlife Conservation Strategy. State of Hawaiʻi. 2005-10-01. Archived from the original (PDF) on 2011-06-16. Retrieved 2009-02-28.
• Guthrie, Julian (2013-06-13). "Larry Ellison's Fantasy Island". Wall Street Journal. Retrieved 2013-06-17.
• "Lanai". Global Volcanism Program. Smithsonian Institution. Retrieved 2021-06-28.