Seán Francis Lemass (15 July 1899 – 11 May 1971) was one of the most prominent Irish politicians of the 20th century. He served as Taoiseach from 1959 until 1966.

A veteran of the 1916 Easter Rising, the War of Independence and the Civil War, Lemass was first elected as a Sinn Féin Teachta Dála (TD) for the Dublin South constituency in a by-election on 18 November 1924 and was returned at each election until the constituency was abolished in 1948, when he was re-elected for Dublin South Central until his retirement in 1969. He was a founding member of Fianna Fáil in 1926, and served as Minister for Industry and Commerce, Minister for Supplies, and Tánaiste in successive Fianna Fáil governments. Lemass is remembered for putting in place innovations to develop Irish industry and for forging new links between the Republic of Ireland and Northern Ireland in the 1960s.

John Francis Lemass was born in Ballybrack, Co. Dublin. He was the second of seven children born to John and Frances Lemass. Within the family his name soon changed to Jack and eventually, after 1916, he himself preferred to be called Seán. He was educated by the Irish Christian Brothers in Dublin, where he was described as studious (his two best subjects being history and mathematics). One of Lemass' classmates was the popular Irish comedian Jimmy O'Dea. Another friend during his youth was Tom Farquharson, who went on to play as a goalkeeper for Cardiff City F.C..

In January 1915 Lemass was persuaded to join the Irish Volunteers. His mature looks ensured he would be accepted as he was only fifteen-and-a-half at the time. Lemass became a member of the A Company of the 3rd Battalion of the Dublin City Regiment. The battalion adjutant was Éamon de Valera, future Taoiseach and President of Ireland. While out on a journey in the Dublin mountains at Easter 1916 Lemass and his brother Noel met two sons of Professor Eoin MacNeill's. They informed the Lemasses of the Easter Rising that was taking place in the city. The following day (Monday) Seán and Noel Lemass were allowed to join the Volunteer garrison at the General Post Office. Seán Lemass was equipped with a shotgun and was positioned on the roof. However, by Friday the Rising had ended in ruins and all involved were imprisoned. Lemass, due to his age, was released from the 1,783 that were arrested. Following this, Lemass' father wanted his son to continue with his studies and to become a barrister.

Until November 1920, Lemass remained a part-time member of the Volunteers. In that month, during the height of the Irish War of Independence, twelve members of the Dublin Brigade of the IRA took part in an attack on British agents living in Dublin, whose names and addresses had been leaked to Collins by his network of spies. The group was under the leadership of Michael Collins. The names of those who carried out Collins' orders on the morning of 21 November 1920 were not disclosed until author Tim Pat Coogan mentioned them in his book on the history of the IRA, published in 1970. Coogan identified Lemass as taking part in the killing of a British agent as a member of "Apostles" entourage that killed fourteen and wounded five British agents of the Cairo Gang. That day, 21 November 1920, became known as the original Bloody Sunday — not to be confused with the 1972 Bloody Sunday in Derry City — when the Black and Tans attacked a Gaelic football game at Croke Park and shot at the crowd and players indiscriminately, murdering fourteen civilians. Lemass was arrested in December 1920, and interned at Ballykinlar, County Down, which would later become part of Northern Ireland.

In December 1921, after the signing of the Anglo-Irish Treaty, Lemass was released. During the debates of the Anglo-Irish Treaty in 1921, Lemass was one of the minority who opposed it along with de Valera. As a protest all the anti-Treaty side withdrew from the Dáil. In the Irish Civil War which followed Lemass was adjutant and second in command to Rory O'Connor when the group seized the Four Courts, the home of the High Court of Ireland. The occupation of the Four Courts eventually resulted in the outbreak of Civil War, when, under British pressure, the Free State side shelled the building on 28 June 1922. As a result, fighting broke out in Dublin between pro and anti Treaty factions. The Four Courts surrendered after two days bombardment, however Lemass escaped with Ernie O'Malley and some others. He was later re-captured and imprisoned again.

In June 1923, after the end of the civil war, Sean Lemass's brother Noel Lemass, an anti-Treaty IRA officer, was abducted in Dublin by a number of men, believed to be connected to the Irish Army or the Police CID unit. He was held in secret until October when his body was found in the Dublin Mountains, Seán Lemass was released from prison on compassionate grounds as a result of this. On 18 November 1924 Lemass was elected for the first time as a Sinn Féin TD.

On 24 August 1924, Lemass married Kathleen Hughes much to the disapproval of the bride's parents. The wedding took place in the Roman Catholic Church of the Holy Name, Ranelagh, Dublin. Jimmy O'Dea, the well known comedian, acted as Lemass's best man.

Together Seán and Kathleen had four children - Maureen (b. 1925), Peggy (1927 – 2004), Noel (1929 – 1976) and Sheila (1932 – 1998). Maureen Lemass would later go on to marry a successor of Lemass as Fianna Fáil leader and a future Taoiseach, Charles Haughey.

In 1926, de Valera, supported by Lemass, sought to convince Sinn Féin to abandon its refusal to accept the existence of the Irish Free State, the legitimacy of the Dáil, and its abstentionist policy of refusing to sit in the Dáil, if elected. However, the effort was unsuccessful and in March 1926 de Valera, along with Lemass, resigned from the party. At this point, de Valera contemplated leaving public life, a decision that would have changed the course of Irish history. It was Lemass who encouraged him to stay and form a political party. In May, de Valera, assisted by Gerald Boland and Lemass, began to plan a new party. This became known as Fianna Fáil – The Republican Party. Lemass travelled around the country trying to raise support for Fianna Fáil. Many former Sinn Féin TDs were persuaded to join. The new party was strongly opposed to partition but accepted the de-facto existence of the Irish Free State. It opposed the controversial Oath of Allegiance and campaigned for its removal: pending its removal, the party announced that it would not take up its Dáil seats. A court case was begun in the name of Lemass and others. However, the assassination by the IRA of Kevin O'Higgins, the Vice-President of the Executive Council (deputy prime minister), led to the passing of a new Act requiring all prospective Dáil candidates to take an oath that, if elected, they would swear the Oath of Allegiance; a refusal to do so would prohibit anyone from candidacy in a general or by-election.

Faced with the threat of legal disqualification from politics, de Valera capitulated and took the Oath of Allegiance while claiming that he was simply signing a slip of paper to gain a right of participation in the Dáil, not actually taking an Oath. On 11 August 1927, having signed the Oath of Allegiance in front of a representative of the Governor-General of the Irish Free State, all the Fianna Fáil TDs entered the Dáil.

In 1932, Fianna Fáil won power in the Free State, remaining in government for 16 uninterrupted years. The party which Lemass had described as only a "slightly constitutional party" in 1929 was now leading the Irish Free State, a state that de Valera and Lemass had fought a civil war to destroy a decade earlier. De Valera appointed Lemass as Minister for Industry and Commerce, one of the most powerful offices in the Executive Council (cabinet), and a position he would occupy in every de Valera government. Lemass had the two difficult tasks of developing Irish industry behind his new tariff walls, and convincing the conservative Department of Finance to promote state involvement in industry. Against the background of the Great Depression, he and de Valera launched the Anglo-Irish Trade War which lasted from 1933 until 1938, causing severe damage and hardship to the Irish economy and the cattle industry. In 1933, Lemass set up the Industrial Credit Corporation to facilitate investment for industrial development; in the climate of the depression investment had dried up. A number of semi-state companies, modelled on the success of the ESB, were also set up. These included the Irish Sugar Company, to develop the sugar-beet industry, Turf Development Board for turf development, and an Irish airline, Aer Lingus. Years later Lemass described Aer Lingus as his "proudest achievement". These helped create management skills within Ireland, as most people of ability preferred to emigrate.

The Irish market was still too small for multiple companies to exist so practically all the semi-states had a monopoly on the Irish market. While Lemass concentrated on economic matters, de Valera focused primarily on constitutional affairs, leading to the passage of the new Constitution of Ireland in 1937. De Valera became Taoiseach, while Lemass served in the new Government (the new name for the cabinet) again as Minister for Industry and Commerce. Lemass became Minister for Supplies in 1939 following the outbreak of World War II (known in Ireland, or Éire, as The Emergency). It was a crucial role for Ireland, which maintained an official neutrality. The state had to achieve an unprecedented degree of self-sufficiency and it was Lemass's role to ensure this; he had the difficult task of organising what little resources existed. In 1941, the Irish Shipping Company was set up to keep a vital trickle of supplies coming into the country. However, petrol, gas, and some foodstuffs remained in short supply. De Valera chose Lemass over older cabinet colleagues to become Tánaiste (deputy prime minister) when Seán T. O'Kelly was elected President of Ireland in 1945.

In 1948, partly due to its own increasing isolation and also due to a republican backlash against its anti-IRA policies (which during the Emergency had seen the execution of IRA prisoners - in part due to IRA links with the Nazis), which had produced a rival republican party, Clann na Poblachta, Fianna Fáil lost power.

The First Inter-Party Government, made up of Fine Gael, the Labour Party, National Labour Party, Clann na Talmhan, Clann na Poblachta and others, was formed under Fine Gael TD John A. Costello. In opposition, Lemass played a crucial role in re-organising and streamlining Fianna Fáil. As a result of this, and also due to crises within the Inter-Party government over the declaration of the Republic of Ireland and the controversial Mother and Child Scheme, Fianna Fáil were not long out of government.

In 1951 Fianna Fáil returned as a minority government. Lemass again returned as Minister for Industry and Commerce. Lemass believed that a new economic policy was needed, however de Valera disagreed. Seán MacEntee, the Minister for Finance, tried to deal with the crisis in the balance of payments. He was also unsympathetic to a new economic outlook. In 1954 the government fell and was replaced by the Second Inter-Party Government.

Lemass was confined to the Opposition benches for another three years. In 1957 de Valera, at the age of seventy-five, announced to Fianna Fáil that he planned to retire. He was persuaded however to become Taoiseach one more time until 1959, when the office of President of Ireland would become vacant. Lemass returned as Tánaiste and Minister for Industry and Commerce. In 1958 the first Programme for Economic Development was launched. De Valera was elected President of Ireland in 1959 and retired as Fianna Fáil leader and Taoiseach.

On 23 June 1959, Seán Lemass was appointed Taoiseach on the nomination of Dáil Éireann. Many had wondered if Fianna Fáil could survive without de Valera as leader. However, Lemass quickly established his control on the party. Although he was one of the founding members of Fianna Fáil he was still only fifty-nine years old, seventeen years younger than the nearly blind de Valera. The change of personnel in Fianna Fáil was also accompanied by a change of personnel with James Dillon becoming leader of Fine Gael and Brendan Corish becoming leader of the Labour Party. A generation of leaders who had dominated Irish politics for over three decades had moved off the stage of history. Lemass also initiated several changes in the Cabinet. He is credited with providing a transition phase between the old guard and a new generation of professional politicians. Younger men such as Brian Lenihan, Charles Haughey, Patrick Hillery, and Michael Hilliard were all given their first Cabinet portolios by Lemass, and ministers who joined under de Valera, such as Jack Lynch, Neil Blaney, and Kevin Boland were promoted by the new Taoiseach. Similarly, several members of the old guard such as Paddy Smith, Seán MacEntee, and James Ryan retired from politics during the Lemass era. Frank Aiken was the only founding member of Fianna Fáil to survive Lemass as a member of the government and the Dáil.

Lemass summed up his economic philosophy by copying an often quoted phrase: "A rising tide lifts all boats." By this he meant that an upsurge in the Irish economy would benefit both the richest and the poorest. Although the White Paper entitled "Economic Development" was first introduced in 1958 in de Valera's last government, its main recommendations formed the basis for the First Programme for Economic Expansion, which was adopted by Lemass as government policy. The programme, which was the brainchild of T.K. Whitaker, involved a move away from the protectionist policies that had been in place since the 1930s. Tax breaks and grants were also to be provided to foreign firms wishing to set up a company in Ireland. The programme also allowed for the spending of £220 million of state capital in investing in an integrated system of national development.

Following the introduction of this programme the policy of protection was eventually ended and the Control of Manufacturers Act, which had been in place since 1932 and had been introduced by Lemass himself, was also abolished. Although the implementation of the programme coincided with favourable trading conditions the results of the programme speak for themselves. Unemployment fell by a third, emigration reduced considerably and the population grew for the first time since the Famine. Agriculture was the only sector which failed to respond to the programme. A second programme was launched in 1963, with even more ambitious targets, but this was discontinued after Lemass left office in 1967.

Professor Tom Garvin has found (2004) that the protectionist policies were first suggested to de Valera by Lemass in a paper written in 1929–30, and then adopted following the change of government in 1932. He considers that Lemass moved the Irish economy away from free trade in the 1930s, and back into it in the 1960s; a costly mistake that affected many thousands of (non-voting) emigrants.

The programme also paved the way for free trade. In 1960 Ireland signed the General Agreement on Tariffs and Trade (GATT), a worldwide agreement to reduce tariffs. In 1961 Ireland applied unsuccessfully for membership of the European Economic Community. Ireland's failure to join was said to be Lemass's biggest regret and disappointment as Taoiseach. Ireland eventually joined in 1973, two years after Lemass's death. 1965 paved the way for the signing of the Anglo-Irish Trade Agreement between Lemass's government and Harold Wilson's government.

As a result of the economic expansion there was an increase in industrialisation and urbanisation. An increase in prosperity also led to a move away from insularity and conservatism in Irish life. This was facilitated in no small part by the establishment of the state television service, Telefís Éireann on 31 December 1961. Television programmes, such as The Late Late Show and imported American and British ones, had a profound effect on a change in attitude. Subjects such as contraception, the Catholic Church and divorce were being discussed openly in a way which previous generations would never have imagined. The pontificate of Pope John XXIII and the Second Vatican Council also had a profound effect on the changing attititudes of Irish Catholics.

1963 saw the first visit of a sitting US President to Ireland. John F. Kennedy, the great-grandson of an Irish emigrant, came on an official visit. His visit seemed to symbolise a new age for the post Famine Irish. During his visit Kennedy visited distant relatives in County Wexford, as well as visiting Dublin, Cork and Limerick. Kennedy later said that his four day visit to Ireland was one of his most enjoyable. Kennedy later personally invited Lemass back to Washington in October of the same year. One month later the young President Kennedy would be dead.

In 1965 a new report called "Investment in Education" was published. After over forty years of independence the report painted a depressing picture of a system where no changes had taken place. Lemass appointed several young and intelligent men to the post of Minister for Education, including Patrick Hillery and George Colley. Under these people a slow process of change eventually began to take place. However, the most innovative change came in 1966 when Donogh O'Malley was appointed minister. Shortly after taking over O'Malley announced that from 1969 all schools up to Intermediate level would be free and free buses would provide transport for the students. This plan had the backing of Lemass, however, O'Malley never discussed this hugely innovative and hugely expensive plan with any other cabinet ministers, least of all the Minister for Finance Jack Lynch. O'Malley had died by the time his brainchild came to fruition.

The failure of the IRA border campaign in the 1950s and the accession of Lemass as Taoiseach heralded a new policy towards Northern Ireland. The new Taoiseach played down the nationalist rhetoric which had done little to further the situation over the previous forty years. As long as the hardline Basil Brooke was Prime Minister of Northern Ireland there was little hope of a rapprochement. However, in 1963 Terence O'Neill, a younger man with a more pragmatic outlook, succeeded as Prime Minister. A friendship had developed between O'Neill's secretary, Jim Malley, and the Irish civil servant, T.K. Whitaker. A series of behind the scenes negotiations resulted in O'Neill issuing an invitation to Lemass to visit him at Stormont in Belfast.

On 14 January 1965, Lemass travelled to Belfast in the utmost of secrecy. The media and even his own Cabinet had not been informed until the very last minute. The meeting got a mixed reaction in the North, however, in the Republic it was a clear indication that the "Irish Cold War" had ended, or a thaw was prevailing at least. Lemass returned the invitation on 9 February of the same year by inviting O'Neill to Dublin. Further meetings between ministers from both parts of the island occurred. The meetings heralded a new (but short-lived) era of optimism, although many unionists felt the 50th Anniversary celebrations of Easter Rising in 1966 were insulting to them. The refusal to acknowledge the civil rights campaign and the outbreak of violence in 1969 ended the optimism.

The Lemass era saw some significant developments in Irish foreign policy. Frank Aiken served as Minister for External Affairs during the whole of Lemass's tenure as Taoiseach. At the United Nations Aiken took an independent stance and backed the admission of the People's Republic of China to the organisation, in spite of huge protests from the United States. Admitted only in 1955, Ireland played a large role at the UN, serving on the Security Council in 1962, condemning Chinese aggression in Tibet and advocating nuclear arms limitation. One of the main areas of foreign policy which emerged during the Lemass years was a debate over Ireland's neutrality. Lemass was always sceptical about remaining neutral, particularly if Ireland were to join the European Economic Community. Aiken was much more in favour of a neutral, independent stance. In 1962 Irish troops embarked on their first peace keeping mission in the First Republic of the Congo. Nine soldiers were killed during this mission.

While Aiken was at the UN Lemass played a major role in pressing for Ireland's membership of the EEC which in many ways became the chief foreign policy consideration during the 1960s.

In 1966 the Republic of Ireland celebrated the 50th anniversary of the 1916 Easter Rising. The celebrations were alleged by some to have undone the good work that resulted from the Lemass-O'Neill meetings. Éamon de Valera, came within 1% of defeat in an Irish presidential election less than two months after the celebrations he played such a central part of. In November 1966, Lemass announced his decision to retire as Fianna Fáil leader and Taoiseach.

On 10 November 1966, he officially announced to the Dáil with his usual penchant for efficiency, "I have resigned." That very day Jack Lynch became the new leader. Lynch was the first Taoiseach that had not come through the Irish War of Independence. Lemass, who had served his country for fifty years, now retired to the backbenches. He remained a TD until 1969.

During the last few years of his leadership Lemass' health began to deteriorate. He had been a heavy pipe smoker all his life, smoking almost a pound of tobacco a week in his later life. At the time of his retirement it was suspected that Lemass had cancer, however this assumption was later disproved. In February 1971, while attending a rugby game at Lansdowne Road, Lemass became unwell. He was rushed to hospital and later told by his doctor that one of his lungs was about to collapse.

On Tuesday, 11 May 1971 Seán Lemass died in the Mater Hospital in Dublin, aged 71. He was afforded a state funeral and was buried in Deansgrange Cemetery.

Lemass remains one of the most highly regarded of Taoisigh, being described even by later Fine Gael Taoisigh Garret FitzGerald and John Bruton as the best holder of the office, and the man whose cabinet leadership style they wished to follow. Some historians have questioned whether Lemass came to the premiership too late, arguing that had he replaced de Valera as Fianna Fáil leader and Taoiseach in 1951 he could have begun the process of reform of Irish society and the industrialisation of the Republic of Ireland a decade earlier than 1959, when he eventually achieved the top governmental job. Others speculate whether he had been able to achieve some of his policy reforms he did initiate in the 1950s precisely because de Valera was still the leader, his opponents being unwilling to challenge him given that he appeared to have de Valera's backing.

What is not in doubt is that Éamon de Valera and Seán Lemass held diametrically different visions of Ireland; de Valera's was of a pastoral rural-based society "given to frugal living", Lemass has a vision of a modern industrialised society, a member of the European Community. Lemass's coolness towards the revival of the Irish language and intellectual agnosticism also contrasted with de Valera's passionate Gaelicism and commitment to traditional Catholicism.