Lal Bahadur was born in Mughal Sarai, United Provinces, British India, to Sharada Srivastava Prasad, a school teacher, who later became a clerk in the Revenue Office at Allahabad, and Ramdulari Devi. When he was three months old, he slipped out of his mother's arms into a cowherder's basket at the ghats of the Ganges. The cowherder, who had no children, took the child as a gift from God and took him home. Lal Bahadur's parents lodged a complaint with the police, who traced the child, and returned him to his parents.

His father died when he was only a year and a half old. His mother took him and his two sisters to her father's house and settled down there. Lal Bahadur stayed at his grandfather Hazari Lal's house till he was ten. He studied up to class IV at Railway School Mughalsarai. Since there was no high school in the town, he was sent to Varanasi, where he stayed with his maternal uncle and joined the Harischandra High School. While in Varanasi, Shastri once went with his friends to see a fair on the other bank of the Ganges. On the way back he had no money for the boat fare. Instead of borrowing from his friends, he jumped into the river and swam to the other bank.

As a boy, Lal Bahadur loved reading books and was fond of Guru Nanak's verses. He revered Bal Gangadhar Tilak, the Indian nationalist, social reformer and freedom fighter. After hearing a speech of Mahatma Gandhi at Varanasi in 1915, he dedicated his life to the service of the country. He also dropped his surname Srivastava as it indicated his caste and he was against the caste system. During the non - cooperation movement of Mahatma Gandhi in 1921, he joined processions in defiance of the prohibitory order. He was arrested but let off as he was a minor. He then enrolled at the nationalist Kashi Vidyapeeth in Varanasi. During his four years there, he was greatly influenced by the lectures of Dr. Bhagawandas on philosophy. Upon completion of his course at Kashi Vidyapeeth in 1926, he was given the title Shastri ("Scholar"). The title was a bachelor's degree awarded by the Vidya Peeth, but it stuck as part of his name. He also enrolled himself as a life member of the Servants of the People Society and began to work for the upliftment of the Harijans at Muzaffarpur. Later he became the President of the Society.

In 1927, Shastri married Lalita Devi of Mirzapur. In spite of the prevailing hefty dowry tradition, Shastri accepted only a charkha and a few yards of khadi as dowry. In 1930, he threw himself into the freedom struggle during Mahatma Gandhi's Salt Satyagraha. He was imprisoned for two and a half years. Once, while he was in prison, one of his daughters fell seriously ill. He was released for fifteen days, on the condition that he not take part in the freedom movement. However, his daughter died before he reached home. After performing the funeral rites, he voluntarily returned to prison, even before the expiration of the period. A year later, he asked for permission to go home for a week, as his son had contracted influenza. The permission was given, but his son's illness was not cured in a week. In spite of his family's pleadings, he kept his promise to the jail officers and returned to the prison.

Later, he worked as the Organizing Secretary of the Parliamentary Board of U.P. in 1937. In 1940, he was sent to prison for one year, for offering individual Satyagraha support to the freedom movement. On 8 August 1942, Mahatma Gandhi issued the Quit India speech at Gowalia Tank in Mumbai, demanding that the British leave India. Shastri, who had just then come out after a year in prison, travelled to Allahabad. For a week, he sent instructions to the freedom fighters from Jawaharlal Nehru's hometown, Anand Bhavan. A few days later, he was arrested and imprisoned until 1946. Shastri spent almost nine years in jail in total. During his stays in prison, he spent time reading books and became familiar with the works of western philosophers, revolutionaries and social reformers. He also translated the autobiography of Marie Curie into Hindi.

Following India's independence, Shastri was appointed Parliamentary Secretary in his home state, Uttar Pradesh. He became the Minister of Police and Transport under Govind Ballabh Pant's Chief Ministership. As the Transport Minister, he was the first to appoint women conductors. As the minister in charge of the Police Department, he ordered that police use jets of water instead of lathis to disperse unruly crowds. In 1951, he was made the General Secretary of the All - India Congress Committee, with Jawaharlal Nehru as the Prime Minister. He was directly responsible for the selection of candidates and the direction of publicity and electioneering activities. He played an important role in the landslide successes of the Congress Party in the Indian General Elections of 1952, 1957 and 1962.

In 1951, Nehru nominated him to the Rajya Sabha. He served as the Minister of Railways and Transport in the Central Cabinet from 1951 to 1956. In 1956, he offered his resignation after a railway accident at Mahbubnagar that led to 112 deaths. However, Nehru did not accept his resignation. Three months later, he resigned accepting moral and constitutional responsibility for a railway accident at Ariyalur in Tamil Nadu that resulted in 144 deaths. While speaking in Parliament on the incident, Nehru stated that he was accepting the resignation because it would set an example in constitutional propriety and not because Shastri was in any way responsible for the accident. Shastri's unprecedented gesture was greatly appreciated by the citizens.

In 1957, Shastri returned to the Cabinet following the General Elections, first as the Minister for Transport and Communications, and then as the Minister of Commerce and Industry. In 1961, he became Minister for Home. As Union Home Minister he was instrumental in appointing the Committee on Prevention of Corruption under the Chairmanship of K. Santhanam.

Jawaharlal Nehru died in office on 27 May 1964 and left a void. The then Congress Party President K. Kamaraj was instrumental in making Shastri Prime Minister on 9 June. Shastri, though mild - mannered and soft - spoken, was a Nehruvian socialist and thus held appeal to those wishing to prevent the ascent of conservative right winger Morarji Desai.

In his first broadcast as Prime Minister, on 11 June 1964, Shastri stated:

"There comes a time in the life of every nation when it stands at the cross - roads of history and must choose which way to go. But for us there need be no difficulty or hesitation, no looking to right or left. Our way is straight and clear — the building up of a socialist democracy at home with freedom and prosperity for all, and the maintenance of world peace and friendship with all nations."

Shastri worked by his natural characteristics to obtain compromises between opposing viewpoints, but in his short tenure he was ineffectual in dealing with the economic crisis and food shortage in the nation. However, he commanded a great deal of respect in the Indian populace, and he used it to gain advantage in pushing the Green Revolution in India, which directly led to India becoming a food - surplus nation, although he did not live to see it. During the 22 day war with Pakistan, Lal Bahadur Shastri created the slogan of "Jai Jawan Jai Kisan" ("Hail the soldier, Hail the farmer"), underlining the need to boost India's food production. Apart from emphasizing the Green Revolution, he was instrumental in promoting the White Revolution. Greatly impressed by a visit to the Kaira district in October 1964, he urged the rest of the country to learn from the successful experiment at Anand. The National Dairy Development Board was formed in 1965 during his tenure as Prime Minister.

Though he was a socialist, Shastri stated that India cannot have a regimented type of economy. During his tenure as Prime Minister, he visited in 1965 Russia, Yugoslavia, England, Canada and Burma.

The dominant problem for Shastri's administration was Pakistan. Laying claim to half of the Kutch peninsula, Pakistan sent incursion forces in August 1965, which skirmished with Indian tank divisions. In his report to the Lok Sabha on the confrontation in Kutch, Shastri stated:

"In the utilization of our limited resources, we have always given primacy to plans and projects for economic development. It would, therefore, be obvious for anyone who is prepared to look at things objectively that India can have no possible interest in provoking border incidents or in building up an atmosphere of strife.... In these circumstances, the duty of Government is quite clear and this duty will be discharged fully and effectively.... We would prefer to live in poverty for as long as necessary but we shall not allow our freedom to be subverted."

Under a scheme proposed in June 1965 by British Prime Minister Harold Wilson, Pakistan obtained 10%, in place of their original claim of 50% of the territory. But Pakistan's aggressive intentions were also focused on Kashmir. When armed infiltrators from Pakistan began entering the State of Jammu and Kashmir, Shastri made it clear to Pakistan that force would be met with force. In September 1965, major incursions of militants and Pakistani soldiers began, hoping not only to break down the government but incite a sympathetic revolt. The revolt did not happen, and India sent its forces across the Ceasefire Line (now Line of Control) and threatened Pakistan by crossing the International Border near Lahore as war broke out on a general scale. Massive tank battles occurred in the Punjab, and while the Pakistani forces made some gains, Indian forces captured the key post at Haji Pir, in Kashmir, and brought the Pakistani city of Lahore under artillery and mortar fire.

On 17 September 1965, while the Indo - Pak war was on, India received a letter from China alleging that the Indian army had set up army equipment in Chinese territory, and India would face China's wrath, unless the equipment was pulled down. In spite of the threat of aggression from China, Shastri declared "China's allegation is untrue. If China attacks India it is our firm resolve to fight for our freedom. The might of China will not deter us from defending our territorial integrity." The Chinese did not respond, but the Indo - Pak war resulted in some 3-4,000 casualties on each side and significant loss of materiel.

The Indo - Pak war ended on 23 September 1965 with a United Nations mandated ceasefire. In a broadcast to the nation on the day the of ceasefire, Shastri stated:

"While the conflict between the armed forces of the two countries has come to an end, the more important thing for the United Nations and all those who stand for peace is to bring to an end the deeper conflict.... How can this be brought about? In our view, the only answer lies in peaceful coexistence. India has stood for the principle of coexistence and championed it all over the world. Peaceful coexistence is possible among nations no matter how deep the differences between them, how far apart they are in their political and economic systems, no matter how intense the issues that divide them."

After the declaration of ceasefire, Shastri and Pakistani President Muhammad Ayub Khan attended a summit in Tashkent (former USSR, now in modern Uzbekistan), organised by Alexei Kosygin. On 10 January 1966, Shastri and Khan signed the Tashkent Declaration.

The next day Shastri, who had suffered two heart attacks earlier, died supposedly of a heart attack at 1:32 AM. He is the only Indian Prime Minister to have died in office overseas.

Although officially it was maintained that Shastri died of heart attack, his widow, Lalita Shastri, persistently alleged that her husband was poisoned. Many believed that Shastri's body's turning blue was evidence of his poisoning. Indeed a Russian butler attending to him was arrested on suspicion of poisoning Shastri, but was later absolved of charges.

In 2009, when Anuj Dhar, author of CIA's Eye on South Asia, asked the Prime Minister's Office under an RTI plea (Right to Information Act), that Shastri's cause of death be made public, the PMO refused to oblige, citing that this could lead to harming of foreign relations, cause disruption in the country and cause breach of parliamentary privileges.

The PMO did reveal however that it had in its possession one document related to Shastri's death, but refused to declassify it. The government also admitted that no post mortem examination had been conducted on him in the USSR, but it did have a report of a medical investigation conducted by Shastri's personal physician Dr. R.N. Chugh and some Russian doctors. Furthermore, the PMO revealed that there was no record of any destruction or loss of documents in the PMO having a bearing on Shastri's death. As of July 2009, the home ministry is yet to respond to queries whether India conducted a postmortem and if the government had investigated allegations of foul play.

Shastri shared very little in common with his predecessor Jawaharlal Nehru. While Shastri preferred peace with Pakistan, writing to a friend after the Indo - Pakistani War in 1965 that the problems between both countries should be settled amicably, he had previously displayed a knack for taking quick and decisive actions during the war. He swiftly took the advice of his commanders, and ordered a strike across the Punjab border. This was in stark contrast to Nehru who in a similar situation in 1962, had refused to call in the air force to relieve the pressure on the ground troops. At the end of the conflict, Shastri flamboyantly posed for a photograph on top of a captured Patton tank.

However, in common with Nehru, Shastri was a secularist who refused to mix religion with politics. In a public meeting held at the Ram Lila grounds in Delhi, a few days after the ceasefire, he complained against a BBC report which claimed that Shastri's identity as a Hindu meant that he was ready for a war with Pakistan. He stated:

"While I am a Hindu, Mir Mushtaq who is presiding over this meeting is a Muslim. Mr. Frank Anthony who has addressed you is a Christian. There are also Sikhs and Parsis here. The unique thing about our country is that we have Hindus, Muslims, Christians, Sikhs, Parsis and people of all other religions. We have temples and mosques, gurdwaras and churches. But we do not bring all this into politics. This is the difference between India and Pakistan. Whereas Pakistan proclaims herself to be an Islamic State and uses religion as a political factor, we Indians have the freedom to follow whatever religion we may choose, and worship in any way we please. So far as politics is concerned, each of us is as much an Indian as the other."

Although Shastri had been a cabinet minister for many years in the 1950s, he was poor when he died. All he owned at the end was an old car, which he had bought in installments from the government and for which he still owed money. He was the first railway minister who resigned from office following a major train accident as he felt moral responsibility.

Shastri was known for his honesty and humility throughout his life. He was the first person to be posthumously awarded the Bharat Ratna, and a memorial "Vijay Ghat" was built for him in Delhi. The Shastri Indo - Canadian Institute was named after Shastri due to his role in promoting scholarly activity between India and Canada. Today Lal Bhadur Shastri Memorial run by Lal Bahadur Shastri National Memorial Trust, is situated next to 10 Janpath his residence as Prime Minister, at 1, Motilal Nehru Place, New Delhi. In 2011, on Shastri’s 45th death anniversary, Uttar Pradesh Government announced the renovation of Shastri’s ancestral house at Ramnagar in Varanasi and revealed plans to convert it into a biographical museum.

In 2005, the Government of India created a chair in his honour in the field of democracy and governance at Delhi University.

Lal Bahadur Shastri had five sons, including Anil Shastri and Sunil Shastri, who are politicians.