Nagaland (/ˈnɑːɡəlænd/) is a state in the north-eastern region of India. It is bordered by the Indian states of Arunachal Pradesh to the north, Assam to the west, Manipur to the south, and the Naga Self-Administered Zone of the Sagaing Region of Myanmar (Burma) to the east. Its capital city is Kohima and its largest city is the twin Chümoukedima–Dimapur. The state has an area of 16,579 square kilometres (6,401 sq mi) with a population of 1,980,602 as per the 2011 Census of India, making it one of the least populated states in India.

Nagaland consists of 16 administrative districts, inhabited by 17 major tribes along with other sub-tribes. Each tribe is distinct in character from the other in terms of customs, language and dress. It is a land of folklore passed down the generations through word of mouth. The earliest recorded history of the Nagas of the present-day Nagaland dates back to the 13th century.

In the 19th century, the British India forces began expanding their influence in Northeast India, including the Naga Hills. After India's independence in 1947, the question of the Naga Hills' political status emerged. Nagaland was a district in the State of Assam until 1957, known to others as "The Naga Hills". The Naga National Council, led by Zapu Phizo, demanded an independent Naga state and launched an armed insurgency. The Indian Government, however, maintained that Nagaland was an integral part of the Indian Union. The conflict between the Naga National Council and the Indian Government resulted in a protracted insurgency. The State of Nagaland was formally inaugurated on 1 December 1963, as the 16th state of the Indian Union, and a democratically elected government took office in 1964.

Nagaland is home to a rich variety of natural, cultural, and environmental resources. It is a mountainous state and lies between the parallels of 95° and 94° eastern longitude and 25.2° and 27.0° latitude north. The high-profile Dzüko Valley is at Viswema, in the southern region of the state. The state has significant resources of natural minerals, petroleum, and hydropower, with the primary sector which is mostly agriculture still accounting for 24.6% of its economy. Other significant activities include forestry, tourism, insurance, real estate, horticulture, and miscellaneous cottage industries.

The origin of the word 'Naga' is unclear. The present day Naga people have historically been referred to by many names, like "Noga" or "Naka" by the inhabitants of the Ahom kingdom in what is now considered as Assam which means "naked", "Hao" by Meitei people of Imphal Valley and "Nakas" or 'Naga' by Burmese of what is now considered as Myanmar meaning "people with earrings", while others suggest it means pierced noses.

Before the arrival of European colonialism in South Asia, there had been many wars, persecution and raids from Burma on the Nagas, Meiteis and others in India's northeast. The invaders came for "head hunting" and to seek wealth and captives from these tribes and ethnic groups. When the British inquired with Burmese guides about the people living in the northern Himalayas, they were told 'Naka'. This was recorded as 'Naga' and has been in use thereafter.

The ancient history of the Nagas is unclear. Ethnic groups migrated at different times, each settling in the northeastern part of present India and establishing their respective sovereign mountain terrains and village states. There are no records of whether they came from the northern Mongolian region, southeast Asia, or southwest China, except that their origins are from the east of India, and historical records show the present-day Naga people settled before the arrival of the Ahoms in 1228 CE.

In Yan-aung-myin Pagoda inscription found in Pinya of Myanmar mentions that the Kingdom of Ava under Minkhaung I (1400–1421) in the early 1400s extended till the territories of the Nagas.

With the arrival of the British East India Company in the early 19th century, followed by the British Raj, Britain expanded its domain over the whole of South Asia, including the Naga Hills. The first Europeans to enter the hills were Captain Francis Jenkins and Lieutenant Robert Pemberton in 1832. The early contact with the Naga ethnic groups was characterised by suspicion and conflict. The colonial interests in Assam, such as managers of tea estates and other trading posts led defensive action against raids from the ethnic groups who were known for their bravery and "head hunting" practices. To put an end to these raids, the British troops recorded 10 military expeditions between 1839 and 1850. In February 1851, at the bloody Battle of Kikrüma, people died on both the British side and the Kikrüma (Naga) side; in the days after the battle, inter-ethnic warfare followed that led to more bloodshed. After that war, the British adopted a policy of caution and non-interference with Naga ethnic groups.

Despite this, colonists continued to move into Naga peoples' territory. Between 1851 and 1865, Naga ethnic groups continued to raid the British in Assam. The British India Government took over the holdings of the East Indian Company following the Indian Rebellion of 1857. The failings and atrocities of the East Indian Company led the British Crown to review its governance structure throughout South Asia including its northeastern region. In 1866, the British India administration established a post at Samaguting with the explicit goal of ending intertribal warfare and tribal raids on property and personnel.

In 1869, Captain Butler was appointed to lead and consolidate the British presence in the Nagaland Hills. In 1878, the headquarters were transferred to Kohima — creating a city that remains an important center of administration, commerce, and culture for Nagaland.

On 4 October 1879, British political agent G. H. Damant went to Khonoma with troops, where he was shot dead with 35 of his team. Kohima was subsequently attacked and the stockade looted. This violence led to a determined effort by the British Raj to return and respond. The subsequent defeat of Khonoma marked the end of serious and persistent ultimatums in the Naga Hills.

Between 1880 and 1922, the British administration consolidated their position over a large area of the Naga Hills and integrated it into its Assam operations. The British administration enforced the rupee as the currency for economic activity and a system of structured ethnic government that was very different from historic social governance practices.

In parallel, since the mid-19th century, Christian missionaries from the United States and Europe, stationed in India, reached into Nagaland and neighbouring states, converting Nagaland's Naga ethnic groups from animism to Christianity.

In 1944, during World War II, the Japanese Army, with the help of the Indian National Army led by Netaji Subhashchandra Bose, invaded through Burma and attempted to take India through Kohima. The population was evacuated. British India soldiers defended the area of Kohima and having lost many of their original force were relieved by British in June 1944. Together the British and Indian troops successfully repelled the Japanese troops. The battle was fought from 4 April to 22 June 1944 from the town of Kohima, coordinated with action at Imphal, Manipur. The Indian National Army lost half their numbers, many through starvation, and were forced to withdraw through Burma.

There is the World War II Cemetery, and the War Museum, in honour of those who died during World War II during the fighting between the British Empire and Japanese troops. Nearly 4,000 British Empire troops died, along with 3,000 Japanese. Many of those who died were Naga people, particularly the Angami Nagas. Near the memorial is the Kohima Cathedral, on Aradura Hill, built with funds from the families and friends of deceased Japanese soldiers. Prayers are held in Kohima for peace and in memory of the fallen of both sides of the battle.

In 1929, a memorandum was submitted to the Simon Statutory Commission, requesting that the Nagas be exempt from reforms and new taxes proposed in British India, should be left alone to determine their own future.

The Naga Memorandum submitted by the Naga Club (which later became the Naga National Council) to the Simon Commission explicitly stated, 'to leave us alone to determine ourselves as in ancient times.'

After the independence of India in 1947, the area remained a part of the province of Assam. Nationalist activities arose among a section of the Nagas. Phizo-led Naga National Council demanded a political union of their ancestral and native groups. The movement led to a series of violent incidents, that damaged government and civil infrastructure, attacked government officials and civilians. The central government sent the Indian Army in 1955, to restore order. In 1957, an agreement was reached between Naga leaders and the Indian government, creating a single separate region of the Naga Hills. The Tuensang frontier was united with this single political region, Naga Hills Tuensang Area (NHTA), and it became an autonomous area under Sixth Schedule to the Constitution of India. It was to be "administered by the Governor as the agent of the President but will be distinct from the North East Frontier Administration".

This was not satisfactory to the Nagas, however, and agitation with violence increased across the state – including attacks on army and government institutions, banks, as well as non-payment of taxes. In July 1960, following discussion between Prime Minister Nehru and the leaders of the Naga People Convention (NPC), a 16-point agreement was arrived at whereby the Government of India recognised the formation of Nagaland as a full-fledged state within the Union of India.

Accordingly, the territory was placed under the Nagaland Transitional Provisions Regulation, 1961 which provided for an Interim body consisting of 45 members to be elected by tribes according to the customs, traditions and usage of the respective tribes. Subsequently, Nagaland attained statehood with the enactment of the state of Nagaland Act in 1962 by the Parliament. The interim body was dissolved on 30 November 1963 and the state of Nagaland was formally inaugurated on 1 December 1963 and Kohima was declared as the state capital. After elections in January 1964, the first democratically elected Nagaland Legislative Assembly was constituted on 11 February 1964.

The rebel activity continued in many Naga inhabited areas both in India and Burma. Ceasefires were announced and negotiations continued, but this did little to stop the violence. In March 1975, a direct presidential rule was imposed by the then Prime Minister Indira Gandhi on the state. In November 1975, some leaders of the largest rebel groups agreed to lay down their arms and accept the Indian constitution, a small group did not agree and continued their insurgent activity. The Nagaland Baptist Church Council played an important role by initiating peace efforts in the 1960s.

In 2004, two powerful bombs were set off on the same day and struck the Dimapur Railway Station and the Hong Kong Market, resulting in 30 deaths and wounding over 100 others in the deadliest terrorist attack in Nagaland to date.

Over the 5-year period of 2009 to 2013, between 0 and 11 civilians died per year in Nagaland from rebellion related activity (or less than 1 death per 100,000 people), and between 3 and 55 militants died per year in inter-factional killings (or between 0 and 3 deaths per 100,000 people).

In early 2017, Nagaland went into a state of civil unrest and protests in response to the announcement to implement 33% women's reservation in the Civic Elections.

On 4 December 2021, a unit of the 21st Para Special Forces of the Indian Army killed six civilian labourers near Oting Village in the Mon District of Nagaland. Eight more civilians and a soldier were killed in subsequent violence. The incident was widely condemned, with many calling out to repeal and revoke the Armed Forces Special Powers Act.

The most recent Nagaland Legislative Assembly election took place on 27 February 2023 to elect the Members of the Legislative Assembly (MLA) in the 60 Assembly Constituencies in the state. A voter turnout of 87% was observed in the election. The election created history by electing two women candidates for the first time in Nagaland — Hekani Jakhalu Kense and Salhoutuonuo Kruse. Both candidates were from the ruling Nationalist Democratic Progressive Party (NDPP). Salhoutuonuo Kruse later became the first woman minister of the Nagaland Legislative Assembly.