Control over Gangetic plains region was of vital importance to the power and stability of all of India's major empires, including the Maurya (320–200 BCE), Kushan (100–250 CE), Gupta (350–600), and Gurjara-Pratihara (650–1036) empires. Following the Huns' invasions that broke the Gupta empire, the Ganges-Yamuna Doab saw the rise of Kannauj. During the reign of Harshavardhana (590–647), the Kannauj empire reached its zenith. It spanned from Punjab in the north and Gujarat in the west to Bengal in the east and Odisha in the south. It included parts of central India, north of the Narmada River and it encompassed the entire Indo-Gangetic plain. Many communities in various parts of India claim descent from the migrants of Kannauj. Soon after Harshavardhana's death, his empire disintegrated into many kingdoms, which were invaded and ruled by the Gurjara-Pratihara empire, which challenged Bengal's Pala Empire for control of the region. Kannauj was several times invaded by the south Indian Rashtrakuta Dynasty, from the 8th century to the 10th century. After the fall of the Pala empire, the Chero dynasty ruled from the 12th century to the 18th century.

Due to dissatisfaction with British rule, a serious rebellion erupted in various parts of North India, which became known as the Indian Rebellion of 1857; Bengal regiment's sepoy stationed at Meerut cantonment, Mangal Pandey, is widely considered as its starting point. After the revolt failed, the British divided the most rebellious regions by reorganising their administrative boundaries, splitting the Delhi region from 'NWFP of Agra' and merging it with Punjab, while the Ajmer–Marwar region was merged with Rajputana and Oudh was incorporated into the state. The new state was called the North Western Provinces of Agra and Oudh, which in 1902 was renamed as the United Provinces of Agra and Oudh. It was commonly referred to as the United Provinces or its acronym UP.

In 1920, the capital of the province was shifted from Allahabad to Lucknow. The high court continued to be at Prayagraj, but a bench was established at Lucknow. Prayagraj continues to be an important administrative base of today's Uttar Pradesh and has several administrative headquarters. Uttar Pradesh continued to be central to Indian politics and was especially important in modern Indian history as a hotbed of the Indian independence movement. Uttar Pradesh hosted modern educational institutions such as the Aligarh Muslim University, Banaras Hindu University and Darul Uloom Deoband. Nationally known figures such as Ram Prasad Bismil and Chandra Shekhar Azad were among the leaders of the movement in Uttar Pradesh, and Motilal Nehru, Jawaharlal Nehru, Madan Mohan Malaviya and Gobind Ballabh Pant were important national leaders of the Indian National Congress.

The All India Kisan Sabha (AIKS) was formed at the Lucknow session of the Congress on 11 April 1936, with the famous nationalist Swami Sahajanand Saraswati elected as its first President, in order to address the longstanding grievances of the peasantry and mobilise them against the zamindari landlords attacks on their occupancy rights, thus sparking the Farmers movements in India. During the Quit India Movement of 1942, Ballia district overthrew the colonial authority and installed an independent administration under Chittu Pandey. Ballia became known as "Baghi Ballia" (Rebel Ballia) for this significant role in India's independence movement.

The sluggish rivers of the bhabhar deepen in this area, their course running through a tangled mass of thick undergrowth. The terai runs parallel to the bhabhar in a thin strip. The entire alluvial plain is divided into three sub-regions. The first in the eastern tract consisting of 14 districts which are subject to periodical floods and droughts and have been classified as scarcity areas. These districts have the highest density of population which gives the lowest per capita land. The other two regions, the central and the western, are comparatively better with a well-developed irrigation system. They suffer from waterlogging and large-scale user tracts. In addition, the area is fairly arid. The state has more than 32 large and small rivers; of them, the Ganges, Yamuna, Saraswati, Sarayu, Betwa, and Ghaghara are larger and of religious importance in Hinduism.

Cultivation is intensive in the state. Uttar Pradesh falls under three agro-climatic zones viz. Middle Gangetic Plains region (Zone–IV), Upper Gangetic Plains region (Zone–V) and Central Plateau and Hills region (Zone–VIII). The valley areas have fertile and rich soil. There is intensive cultivation on terraced hill slopes, but irrigation facilities are deficient. The Siwalik Range which forms the southern foothills of the Himalayas, slopes down into a boulder bed called 'bhabhar'. The transitional belt running along the entire length of the state is called the terai and bhabhar area. It has rich forests, cutting across it are innumerable streams which swell into raging torrents during the monsoon.

The rain in Uttar Pradesh can vary from an annual average of 170 cm in hilly areas to 84 cm in Western Uttar Pradesh. Given the concentration of most of this rainfall in the four months of the monsoon, excess rain can lead to floods and shortage to droughts. As such, these two phenomena, floods and droughts, commonly recur in the state. The climate of the Vindhya Range and plateau is subtropical with a mean annual rainfall between 1000 and 1200 mm, most of which comes during the monsoon. Typical summer months are from March to June, with maximum temperatures ranging from 30 to 38 °C (86 to 100 °F). There is a low relative humidity of around 20% and dust-laden winds blow throughout the season. In summer, hot winds called loo blow all across Uttar Pradesh.

This plain supports a wide variety of plants and animals. The Ganges and its tributaries are the habitat of large and small reptiles, amphibians, fresh-water fish, and crabs. Scrubland trees such as the Babool (Vachellia nilotica) and animals such as the Chinkara (Gazella bennettii) are found in the arid Vindhyas. Notable indigenous trees are the astringent Azadirachta indica, or neem, which is widely used in rural Indian herbal medicine and the luxuriant Ficus religiosa, or peepul, consider the tree to be sacred by Hindu and Jain ascetics as this is the tree under which Gautama Buddha is believed to have attained enlightenment.

Tropical dry deciduous forests are found in all parts of the plains. Since much sunlight reaches the ground, shrubs and grasses are also abundant. Large tracts of these forests have been cleared for cultivation. Tropical thorny forests, consisting of widely scattered thorny trees, mainly babool are mostly found in the southwestern parts of the state. These forests are confined to areas which have low annual rainfall (50–70 cm), a mean annual temperature of 25–27 °C and low humidity.

Uttar Pradesh is known for its extensive avifauna. The most common birds which are found in the state are doves, peafowl, junglefowl, black partridges, house sparrows, songbirds, blue jays, parakeets, quails, bulbuls, comb ducks, kingfishers, woodpeckers, snipes, and parrots. Bird sanctuaries in the state include Bakhira Sanctuary, National Chambal Sanctuary, Chandra Prabha Sanctuary, Hastinapur Sanctuary, Kaimoor Sanctuary, and Okhla Sanctuary.

Other animals in the state include reptiles such as lizards, cobras, kraits, and gharials. Among the wide variety of fishes, the most common ones are mahaseer and trout. Some animal species in Uttar Pradesh have gone extinct in recent years, while others, like the lion from the Gangetic Plain, the rhinoceros from the Terai region, Ganges river dolphin primarily found in the Ganges have become endangered. Many species are vulnerable to poaching despite regulation by the government.

The sex ratio in 2011, at 912 women to 1000 men, was lower than the national figure of 943. The state's 2001–2011 decennial growth rate (including Uttrakhand) was 20.1%, higher than the national rate of 17.64%.Uttar Pradesh has a large number of people living below the poverty line. As per World Bank document (released in 2016), the pace of poverty reduction in the state has been slower than the rest of the country.[ Estimates released by the Reserve Bank of India for the year 2011–12 revealed that Uttar Pradesh had 59 million people below the poverty line, the most for any state in India. The central and eastern districts in particular have very high levels of poverty. The state is also experiencing widening consumption inequality. As per the report of the Ministry of Statistics and Programme Implementation (released on 7 January 2020), the state per capita income is below ₹8,000 (US$100) per annum.

As per 2011 census, Uttar Pradesh, the most populous state in India, is home to the highest numbers of both Hindus and Muslims. By religion, the population in 2011 was Hindus 79.7%, Muslims 19.3%, Sikhs 0.3%, Christians 0.2%, Jains 0.1%, Buddhists 0.1%, and others 0.3%.The literacy rate of the state at the 2011 census was 67.7%, which was below the national average of 74%.The literacy rate for men is 79% and for women 59%. In 2001 the literacy rate in Uttar Pradesh stood at 56% overall, 67% for men and 43% for women. A report based on a National Statistical Office survey reveals that Uttar Pradesh's literacy rate is 73%—less than the national average of 77.7%. According to the report, in the rural region, the literacy rate among men is 80.5% and women is 60.4%, while in urban areas, the literacy rate among men is 86.8% and women is 74.9%.

Hindi is the official language of Uttar Pradesh and is spoken by the majority of the population (80.16%). But most people speak regional languages classified as dialects of Hindi in the census. These include Awadhi spoken in Awadh in central Uttar Pradesh, Bhojpuri spoken in Purvanchal in eastern Uttar Pradesh, and Braj Bhasha spoken in the Braj region in Western Uttar Pradesh. Urdu is given the status of a second official language, spoken by 5.4% of the population. Other notable languages spoken in the state include Punjabi (0.3%) and Bengali (0.1%).

State industries are localised in the Kanpur region, the fertile purvanchal lands and the Noida region. The Mughalsarai is home to several major locomotive plants. Major manufacturing products include engineering products, electronics, electrical equipment, cables, steel, leather, textiles, jewellery, frigates, automobiles, railway coaches, and wagons. Meerut is the sports capital of India and also a jewellery hub. More small-scale industrial units is situated in Uttar Pradesh than in any other state, with 12 per cent of over 2.3 million units. With 359 manufacturing clusters, cement is the top sector of SMEs in Uttar Pradesh. The Uttar Pradesh Financial Corporation (UPFC) was established in the year 1954 under the SFCs Act of 1951 mainly to develop small- and medium-scale industries in the state. The UPFC also provides working capital to existing units with a sound track record and to new units under a single window scheme. In July 2012, due to financial constraints and directions from the state government, lending activities have been suspended except for State Government Schemes.The state has reported total private investment worth over Rs. 25,081 crores during the years of 2012 and 2016. According to a recent report of World Bank on Ease of Doing Business in India, Uttar Pradesh was ranked among the top 10 states and first among Northern states.

According to the Uttar Pradesh Budget Documents (2019–20), Uttar Pradesh's debt burden is 29.8 per cent of the GSDP. The state's total financial debt stood at ₹2,000 billion (US$26 billion) in 2011. Uttar Pradesh has not been able to witness double digit economic growth despite consistent attempts over the years. The GSDP is estimated to have grown 7 per cent in 2017–18 and 6.5 per cent in 2018–19 which is about 10 per cent of India's GDP. According to a survey conducted by the Centre for Monitoring Indian Economy (CMIE), Uttar Pradesh's unemployment rate increased 11.4 percentage points, rising to 21.5 per cent in April 2020. Uttar Pradesh has the largest number of net migrants migrating out of the state. The 2011 census data on migration shows that nearly 14.4 million (14.7%) people had migrated out of Uttar Pradesh. Marriage was cited as the predominant reason for migration among females. Among males the most important reason for migration was Work / Employment.

In 2009–10, the tertiary sector of the economy (service industries) was the largest contributor to the gross domestic product of the state, contributing 44.8% of the state domestic product compared to 44% from the primary sector (agriculture, forestry, and tourism) and 11.2% from the secondary sector (industrial and manufacturing). MSME sector is the second-largest employment generator in Uttar Pradesh, the first being agriculture and employs over 9.2 million people across the state. Under the leadership of Akhilesh Yadav, Uttar Pradesh has exceeded 11 five-year plan targets and has established several Micro Small and Medium Enterprises (MSMEs) and generated 650,000 employment opportunities across the state. During the 11th five-year plan (2007–2012), the average gross state domestic product (GSDP) growth rate was 7.3%, lower than 15.5%, the average for all states of the country. The state's per capita GSDP was ₹29,417 (US$390), lower than the national per capita GSDP of ₹60,972 (US$800). Labour efficiency is higher at an index of 26 than the national average of 25. Textiles and sugar refining, both long-standing industries in Uttar Pradesh, employ a significant proportion of the state's total factory labour. The economy also benefits from the state's tourism industry. The state's exports include footwear, leather goods, and sporting gear.

The state is attracting foreign direct investment which has mostly come in the software and electronics fields; Noida, Kanpur and Lucknow are becoming major hubs for the information technology (IT) industry and house the headquarters of most of the major corporate, media and financial institutions. Sonebhadra, a district in eastern Uttar Pradesh, has large-scale industries. Its southern region is known as the Energy Capital of India. In May 2013 Uttar Pradesh had the largest number of mobile subscribers in the country, a total of 121.60 million mobile phone connections out of 861.66 million in India, according to the telecom regulator, Telecom Regulatory Authority of India (TRAI). In November 2015, the Ministry of Urban Development selected sixty-one cities of Uttar Pradesh for a comprehensive development program known as the Atal Mission for Rejuvenation and Urban Transformation (AMRUT). A package of ₹260 billion (US$3.4 billion) was declared for the cities to develop service level improvement plan (SLIP), a plan for better functioning of the local urban bodies in the cities.

Religious tourism plays a significant role in Uttar Pradesh tourism as the state has some of the holiest Hindu shrines. Varanasi a major religious hub, is the holiest of the seven sacred cities (Sapta Puri) in Hinduism and Jainism. Domestic tourists most commonly visit for religious purposes while foreign tourists visit for ghats along the river Ganges. Vrindavan is considered to be a holy place for Vaisnavism. Owing to the belief as to the birthplace of Rama, Ayodhya (Awadh) has been regarded as one of the seven most important pilgrimage sites. Millions gather at Allahabad to take part in the Magh Mela festival on the banks of the Ganges. This festival is organised on a larger scale every 12th year and is called the Kumbh Mela, where over 10 million Hindu pilgrims congregate in one of the largest gatherings of people in the world. Vindhyachal is a Hindu pilgrimage site having the temple of Vindhyavasini.

Buddhist attractions in Uttar Pradesh include stupas and monasteries. The historically important towns of Sarnath where Gautama Buddha gave his first sermon after his enlightenment and died at Kushinagar; both are important pilgrimage sites for Buddhists. Also at Sarnath are the Pillars of Ashoka and the Lion Capital of Ashoka, both important archaeological artefacts with national significance. At a distance of 80 km from Varanasi, Ghazipur is famous not only for its Ghats on the Ganges but also for the tomb of Lord Cornwallis, the 18th-century Governor of East India Company ruled Bengal Presidency. The tomb is maintained by the Archaeological Survey of India. The state has one National Park and 25 Wildlife Sanctuaries. Okhla Bird Sanctuary known as a haven for over 300 bird species out of which 160 bird species are migratory, travelling from Tibet, Europe & Siberia and Patna Bird Sanctuary in Etah district, is a major tourist attraction.

Other festivals are Eid-ul-Fitr, Eid-ul-Adhaa/Bakreed, Vijayadashami, Makar Sankranti, Vasant Panchami, Ayudha Puja, Janmashtami, Sardhana Christian Fair, Maha Shivaratri, Mahavir Janma Kalyanak, Ayurved Jhansi Mahotsav, Bārah Wafāṭ, Chhath puja, Lucknow Mahotsav, Moharram, Kabob and Hanuman Jayanti.