West Bengal (, Bengali: Poshchim Bongo, pronounced [ˈpoʃtʃim ˈbɔŋɡo] (listen), abbr. WB) is a state in the eastern region of India along the Bay of Bengal. With over 91 million inhabitants, it is the fourth-most populous state and the thirteenth-largest state by area in India. Covering an area of 88,752 km2 (34,267 sq mi), it is also the eighth-most populous country subdivision of the world. Part of the Bengal region of the Indian subcontinent, it borders Bangladesh in the east, and Nepal and Bhutan in the north. It also borders the Indian states of Odisha, Jharkhand, Bihar, Sikkim and Assam. The state capital is Kolkata, the third-largest metropolis, and seventh largest city by population in India. West Bengal includes the Darjeeling Himalayan hill region, the Ganges delta, the Rarh region, the coastal Sundarbans and the Bay of Bengal. The state's main ethnic group are the Bengalis, with the Bengali Hindus forming the demographic majority. The area's early history featured a succession of Indian empires, internal squabbling, and a tussle between Hinduism and Buddhism for dominance. Ancient Bengal was the site of several major Janapadas, while the earliest cities date back to the Vedic period. The region was part of several ancient pan−Indian empires, including the Vangas, Mauryans, and the Guptas. The citadel of Gauḍa served as the capital of the Gauḍa Kingdom, the Pala Empire, and the Sena Empire. Islam was introduced through trade with the Abbasid Caliphate, but following the Ghurid conquests led by Bakhtiyar Khalji and the establishment of the Delhi Sultanate, the Muslim faith spread across the entire Bengal region. During the Bengal Sultanate, the territory was a major trading nation in the world, and was often referred by the Europeans as the "richest country to trade with". It was absorbed into the Mughal Empire in 1576. Simultaneously, some parts of the region were ruled by several Hindu states, and Baro-Bhuyan landlords, and part of it was briefly overrun by the Suri Empire. Following the death of Emperor Aurangzeb in the early 1700s, the proto-industrialised Mughal Bengal became a semi-independent state under the Nawabs of Bengal, and showed signs of the first Industrial revolution. The region was later conquered by the British East India Company at the Battle of Plassey in 1757 and became part of the Bengal Presidency.The region was a hotbed of the Indian independence movement and has remained one of India's great artistic and intellectual centres. Following widespread religious violence, the Bengal Legislative Council and the Bengal Legislative Assembly voted on the Partition of Bengal in 1947 along religious lines into two independent dominions: West Bengal, a Hindu-majority Indian state, and East Bengal, a Muslim-majority province of Pakistan which later became the independent Bangladesh. Post Indian independence, West Bengal's economy is based on agricultural production and small and medium-sized enterprises. For many decades the state underwent political violence and economic stagnation. In 2020–21, the economy of West Bengal is the sixth-largest state economy in India with a gross state domestic product (GSDP) of ₹13.54 lakh crore (US$170 billion), and has the country's 20th-highest GSDP per capita of ₹121,267 (US$1,500).West Bengal also has the 28th-highest ranking among Indian states in human development index, with the index value being less than that of India. The state government debt of ₹4.8 lakh crore (US$60 billion), or 35.54% of GSDP, is fifth highest India, but has dropped from 40.65% since 2010–11. There is moderate unemployment. West Bengal has two World Heritage sites and ranks as the seventh-most visited tourist destination in India.

Cooch Behar, also known as Koch Bihar, was a princely state in India during the British Raj. The state was placed under the Bengal States Agency, part of the Eastern States Agency of the Bengal Presidency. It is located south of the Himalayan kingdom of Bhutan, in present-day West Bengal. Cooch Behar State was formed when the Kamata Kingdom under the Koch dynasty split following the death of Nara Narayan in 1586. The eastern portion, Koch Hajo, was soon absorbed by Ahom. The western portion, Koch Bihar, formed a separate unit that came under direct challenge by the Mughal Empire. After weathering the Mughal threat, a new foe emerged in the form of an expansionist Bhutanese kingdom. After a series of wars with the Bhutanese and Tibetans, the Northern threat was pushed back but not before a Bhutanese regent was installed in the royal court. The Koch Bihar court decided to invite British intervention. This came in the form of military assistance that—acting in concert with Koch Bihar forces—ended the Northern challenge once and for all. However the British East India Company sought guarantees whereby the independence of Koch Bihar was limited by treaties. When the British colonial rule was finally terminated in India, the Koch Bihar state immediately acceded to and merged with India in 1949 and became a part of West Bengal. The district, Cooch Behar District, is named after this erstwhile kingdom.