The kingdom of Magadha was formed in the 7th century BCE, consisting of the regions now comprising Bihar and Bengal. It was one of the four main kingdoms of India at the time of the lives of Mahavira, the principal figure of Jainism and Gautama Buddha, founder of Buddhism. It consisted of several janapadas, or kingdoms. Under Ashoka, the Maurya Empire of Magadha in the 3rd century BCE extended over nearly all of South Asia, including Afghanistan and parts of Balochistan. From the 3rd to the 6th centuries CE, the kingdom of Magadha served as the seat of the Gupta Empire.

Two kingdoms—Vanga or Samatata, and Gauda—are said in some texts to have appeared after the end of the Gupta Empire although details of their ascendancy are uncertain. The first recorded independent king of Bengal was Shashanka, who reigned in the early 7th century. Shashanka is often recorded in Buddhist annals as an intolerant Hindu ruler noted for his persecution of the Buddhists. He murdered Rajyavardhana, the Buddhist king of Thanesar, and is noted for destroying the Bodhi tree at Bodhgaya, and replacing Buddha statues with Shiva lingams. After a period of anarchy, the Pala dynasty ruled the region for four hundred years beginning in the 8th century. A shorter reign of the Hindu Sena dynasty followed.

Rajendra Chola I of the Chola dynasty invaded some areas of Bengal between 1021 and 1023.

Islam was introduced through trade with the Abbasid Caliphate. Following the Ghurid conquests led by Muhammad bin Bakhtiyar Khalji and the establishment of the Delhi Sultanate, it spread across the entire Bengal region. Mosques, madrasas and khanqahs were built throughout these stages. During the Islamic Bengal Sultanate, founded in 1352, Bengal was a major world trading nation and was often referred by the Europeans as the richest country with which to trade. Later, in 1576, it was absorbed into the Mughal Empire.

Following the death of Emperor Aurangzeb and the Governor of Bengal, Shaista Khan, the proto-industrialised Mughal Bengal became a semi-independent state under the Nawabs of Bengal, and showed signs of the world's first Industrial revolution.The Koch dynasty in northern Bengal flourished during the 16th and 17th centuries; it weathered the Mughals and survived until the advent of the British colonial era.

The Bengal Renaissance and the Brahmo Samaj socio-cultural reform movements significantly influenced the cultural and economic life of Bengal. Between 1905 and 1911 an abortive attempt was made to divide the province of Bengal into two zones.Bengal suffered from the Great Bengal famine in 1943, which claimed three million lives during World War II.

Bengalis played a major role in the Indian independence movement, in which revolutionary groups such as Anushilan Samiti and Jugantar were dominant. Armed attempts against the British Raj from Bengal reached a climax when news of Subhas Chandra Bose leading the Indian National Army against the British reached Bengal. The Indian National Army was subsequently routed by the British.

During the 1970s and 1980s, severe power shortages, strikes and a violent Marxist–Maoist movement by groups known as the Naxalites damaged much of the city's infrastructure, leading to a period of economic stagnation and deindustrialization. The Bangladesh Liberation War of 1971 resulted in an influx of millions of refugees to West Bengal, causing significant strains on its infrastructure. The 1974 smallpox epidemic killed thousands. West Bengal politics underwent a major change when the Left Front won the 1977 assembly election, defeating the incumbent Indian National Congress. The Left Front, led by the Communist Party of India (Marxist), governed the state for the next three decades.

The state's economic recovery gathered momentum after the central government introduced economic liberalisations in the mid-1990s. This was aided by the advent of information technology and IT-enabled services. Beginning in the mid-2000s, armed activists conducted minor terrorist attacks in some parts of the state. Clashes with the administration took place at several controversial locations over the issue of industrial land acquisition. This became a decisive reason behind the defeat of the ruling Left Front government in the 2011 assembly election. Although the economy was severely damaged during the unrest in the 1970s, the state has managed to revive its economy steadily throughout the years. The state has shown improvement regarding bandhs (strikes) and educational infrastructure. Significant strides have been made in reducing unemployment, though the state suffers from substandard healthcare services, a lack of socio-economic development, poor infrastructure, unemployment and civil violence. In 2006 the state's healthcare system was severely criticised in the aftermath of the West Bengal blood test kit scam.

From a phytogeographic viewpoint, the southern part of West Bengal can be divided into two regions: the Gangetic plain and the littoral mangrove forests of the Sundarbans. The alluvial soil of the Gangetic plain, combined with favourable rainfall, makes this region especially fertile. Much of the vegetation of the western part of the state has similar species composition with the plants of the Chota Nagpur plateau in the adjoining state of Jharkhand. The predominant commercial tree species is Shorea robusta, commonly known as the sal tree. The coastal region of Purba Medinipur exhibits coastal vegetation; the predominant tree is the Casuarina. A notable tree from the Sundarbans is the ubiquitous sundari (Heritiera fomes), from which the forest gets its name.

The distribution of vegetation in northern West Bengal is dictated by elevation and precipitation. For example, the foothills of the Himalayas, the Dooars, are densely wooded with sal and other tropical evergreen trees. Above an elevation of 1,000 metres the forest becomes predominantly subtropical. In Darjeeling, which is above 1,500 metres (4,900 ft), temperate forest trees like oaks, conifers and rhododendrons predominate.

3.26% of the geographical area of West Bengal is protected land, comprising fifteen wildlife sanctuaries and five national parks—Sundarbans National Park, Buxa Tiger Reserve, Gorumara National Park, Neora Valley National Park and Singalila National Park. Extant wildlife includes Indian rhinoceros, Indian elephant, deer, leopard, gaur, tiger and crocodiles, as well as many bird species. Migratory birds come to the state during the winter. The high-altitude forests of Singalila National Park shelter barking deer, red panda, chinkara, takin, serow, pangolin, minivet and kalij pheasants. The Sundarbans are noted for a reserve project devoted to conserving the endangered Bengal tiger, although the forest hosts many other endangered species such as the Gangetic dolphin, river terrapin and estuarine crocodile. The mangrove forest also acts as a natural fish nursery, supporting coastal fishes along the Bay of Bengal. Recognising its special conservation value, the Sundarbans area has been declared a Biosphere Reserve.

In 2015–2016, the percentage share of Gross Value Added (GVA) at factor cost by economic activity at the constant price (the base year 2011–2012) was Agriculture-Forestry and Fishery—4.84%, Industry 18.51% and Services 66.65%. It has been observed that there has been a slow but steady decline in the percentage share of industry and agriculture over the years. Agriculture is the leading economic sector in West Bengal. Rice is the state's principal food crop. Rice, potato, jute, sugarcane and wheat are the state's top five crops. Tea is produced commercially in northern districts; the region is well known for Darjeeling and other high-quality teas. State industries are localised in the Kolkata region, the mineral-rich western highlands, and the Haldia Port region.The Durgapur-Asansol colliery belt is home to a number of steel plants. Important manufacturing industries include: engineering products, electronics, electrical equipment, cables, steel, leather, textiles, jewellery, frigates, automobiles, railway coaches and wagons. The Durgapur centre has established several industries in the areas of tea, sugar, chemicals and fertilisers. Natural resources like tea and jute in nearby areas have made West Bengal a major centre for the jute and tea industries.

Years after independence, West Bengal is dependent on the central government for help in meeting its demands for food; food production remained stagnant, and the Indian green revolution bypassed the state. However, there has been a significant increase in food production since the 1980s and the state now has a surplus of grains. The state's share of total industrial output in India was 9.8% in 1980–1981, declining to 5% by 1997–1998. In contrast, the service sector has grown at a rate higher than the national rate. The state's total financial debt stood at ₹1,918,350 million (US$25 billion) as of 2011.

In the period 2004–2010, the average gross state domestic product (GSDP) growth rate was 13.9% lower than 15.5%, the average for all states of the country.

The economy of West Bengal has witnessed many surprising changes in direction. The agricultural sector in particular rose to 8.33% in 2010–11 before tumbling to −4.01% in 2012–13. Many major industries such as the Uttarpara Hindustan Motors car manufacturing unit, the jute industry, and the Haldia Petrochemicals unit experienced shutdowns in 2014. In the same year, plans for a 300 billion Jindal Steel project was mothballed. The tea industry of West Bengal has also witnessed shutdowns for financial and political reasons. The tourism industry of West Bengal was negatively impacted in 2017 because of the Gorkhaland agitation.

However, over the years due to effective changes in the stance towards industrialisation, ease of doing business has improved in West Bengal. Steps are being taken to remedy this situation by promoting West Bengal as an investment destination. A leather complex has been built in Kolkata. Smart cities are being planned close to Kolkata, and major roadway projects are in the offing to revive the economy. West Bengal has been able to attract 2% of the foreign direct investment in the last decade.

The literacy rate is 77.08%, higher than the national rate of 74.04%. Data from 2010 to 2014 showed the life expectancy in the state was 70.2 years, higher than the national value of 67.9. The proportion of people living below the poverty line in 2013 was 19.98%, a decline from 31.8% a decade ago. Scheduled castes and tribes form 28.6% and 5.8% of the population, respectively, in rural areas and 19.9% and 1.5%, respectively, in urban areas.

In September 2017, West Bengal achieved 100% electrification, after some remote villages in the Sunderbans became the last to be electrified.

As of September 2017, of 125 towns and cities in Bengal, 76 have achieved open defecation free (ODF) status. All towns in the districts of: Nadia, North 24 Parganas, Hooghly, Bardhaman and East Medinipur are ODF zones, with Nadia becoming the first ODF district in the state in April 2015.

A study conducted in three districts of West Bengal found that accessing private health services to treat illness had a catastrophic impact on households. This indicates the importance of the public provision of health services to mitigate poverty and the impact of illness on poor households.

The latest Sample Registration System (SRS) statistical report shows that West Bengal has the lowest fertility rate among Indian states. West Bengal's total fertility rate was 1.6, lower than Bihar's 3.4, which is the highest in the entire country. Bengal's TFR of 1.6 roughly equals that of Canada.

Bengalis, consisting of Bengali Hindus, Bengali Muslims, Bengali Christians and a few Bengali Buddhists, comprise the majority of the population. Marwari, Maithili and Bhojpuri speakers are scattered throughout the state; various indigenous ethnic Buddhist communities such as the Sherpas, Bhutias, Lepchas, Tamangs, Yolmos and ethnic Tibetans can be found in the Darjeeling Himalayan hill region. Native Khortha speakers are found in Malda district. Surjapuri, a language considered to be a mix of Maithili and Bengali, is spoken across northern parts of the state. The Darjeeling Hills are mainly inhabited by various Gorkha communities who overwhelmingly speak Nepali (also known as Gorkhali), although there are some who retain their ancestral languages like Lepcha. West Bengal is also home to indigenous tribal Adivasis such as: Santhal, Munda, Oraon, Bhumij, Lodha, Kol and Toto. There are a small number of ethnic minorities primarily in the state capital, including : Chinese, Tamils, Maharashtrians, Odias, Malayalis, Gujaratis, Anglo-Indians, Armenians, Jews, Punjabis and Parsis. India's sole Chinatown is in eastern Kolkata.