Markievicz was born Constance Georgine Gore-Booth at Buckingham Gate in London, the elder daughter of the Arctic explorer and adventurer Sir Henry Gore-Booth, 5th Baronet, an Anglo-Irish landlord who administered a 100 km2 (39 sq mi) estate, and Georgina, Lady Gore-Booth née Hill. During the famine of 1879–80, Sir Henry provided free food for the tenants on his estate at Lissadell House in the north of County Sligo in the north-west of Ireland. Their father's example inspired in Gore-Booth and her younger sister, Eva Gore-Booth, a deep concern for working people and the poor. The sisters were childhood friends of the poet W. B. Yeats, who frequently visited the family home Lissadell House, and were influenced by his artistic and political ideas. Yeats wrote a poem, "In Memory of Eva Gore-Booth and Con Markiewicz", in which he described the sisters as "two girls in silk kimonos, both beautiful, one a gazelle" (the gazelle being Constance). Eva later became involved in the labour movement and women's suffrage in England, although initially Constance did not share her sister's ideals.
Gore-Booth decided to train as a painter, but, at the time, only one art school in Dublin accepted female students. In 1892, she went to study at the Slade School of Art in London. It was at this time that Gore-Booth first became politically active and joined the National Union of Women's Suffrage Societies (NUWSS). Later she moved to Paris and enrolled at the prestigious Académie Julian where she met her future husband, Casimir Markievicz, an artist from a wealthy Polish family from Ukraine. Markievicz was known in Paris as "Count Markievicz". When Constance's family enquired as to the validity of the title, they were informed through Pyotr Rachkovsky of the Russian Secret Police that he had taken the title "without right", and that there had never been a "Count Markievicz" in Poland. (An online list of counts of the imperial Russian nobility does not include anybody by the name of Markiewicz.) However, the Department of Genealogy in Saint Petersburg said that he was entitled to claim to be a member of the nobility. Markievicz was married, though separated, at the time that they met, but his wife died in 1899 and he and Gore-Booth married in London on 29 September 1900. She was afterwards known as "Countess Markievicz". She gave birth to their daughter, Maeve, at Lissadell in November 1901. The child was raised by her Gore-Booth grandparents and eventually became estranged from her mother. She undertook the role of mother to Stanislas, Casimir's son from his first marriage, who then accompanied the couple to Ireland.
The Markieviczes settled in Dublin in 1903 and moved in artistic and literary circles, with Constance gaining a reputation as a landscape painter. In 1905, along with artists Sarah Purser, Nathaniel Hone, Walter Osborne and John Butler Yeats, she was instrumental in founding the United Arts Club, which was an attempt to bring together all those in Dublin with an artistic and literary bent. This group included the leading figures of the Gaelic League founded by the future first President of Ireland, Douglas Hyde. Although formally apolitical and concerned with the preservation of the Irish language and culture, the league brought together many patriots and future political leaders. Sarah Purser, whom the young Gore-Booth sisters first met in 1882, when she was commissioned to paint their portrait, hosted a regular salon where artists, writers and intellectuals on both sides of the nationalist divide gathered. At Purser's house, Markievicz met revolutionary patriots Michael Davitt, John O'Leary and Maud Gonne. In 1906, Markievicz rented a cottage in the countryside near Dublin. The previous tenant, the poet Padraic Colum, had left behind copies of The Peasant and Sinn Féin. These revolutionary journals promoted independence from British rule. Markievicz read these publications and was propelled into action.
In 1908, Markievicz became actively involved in nationalist politics in Ireland. She joined Sinn Féin and Inghinidhe na hÉireann ('Daughters of Ireland'), a revolutionary women's movement founded by the actress and activist Maud Gonne, muse of W. B. Yeats. Markievicz came directly to her first meeting from a function at Dublin Castle, the seat of British rule in Ireland, wearing a satin ball-gown and a diamond tiara. Naturally, the members looked upon her with some hostility. This refreshing change from being "kowtowed"-to as a countess only made her more eager to join. She performed with Maud Gonne in several plays at the newly established Abbey Theatre, an institution that played an important part in the rise of cultural nationalism. In the same year, Markievicz played a dramatic role in the women's suffrage campaigners' tactic of opposing Winston Churchill's election to Parliament during the Manchester North West by-election, flamboyantly appearing in the constituency driving an old-fashioned carriage drawn by four white horses to promote the suffragist cause. A male heckler asked her if she could cook a dinner, to which she responded, "Yes. Can you drive a coach and four?" Her sister Eva had moved to Manchester to live with fellow suffragette Esther Roper and they both campaigned against Churchill with her. Churchill lost the election to Conservative candidate William Joynson-Hicks, in part as a result of the suffragists' dedicated opposition.
In 1909 Markievicz and Bulmer Hobson founded Fianna Éireann, a para-military nationalist scouting organisation that instructed teenage boys in the use of firearms. At its first meeting in Camden Street, Dublin, on 16 August 1909, she was almost expelled on the basis that women did not belong in a physical force movement, but Hobson supported her, and she was elected to the committee. She was jailed for the first time in 1911 for speaking at an Irish Republican Brotherhood demonstration attended by 30,000 people, organised to protest against George V's visit to Ireland. During this protest Markievicz handed out leaflets, erected great masts: Dear land thou art not conquered yet., participated in stone-throwing at pictures of the King and Queen and attempted to burn the giant British flag taken from Leinster House, eventually succeeding, but then seeing James McArdle imprisoned for one month for the incident, despite Markievicz testifing in court that she was responsible. Her friend Helena Molony was arrested for her part in the stone-throwing and became the first woman in Ireland to be tried and imprisoned for a political act since the time of the Ladies Land League.
Markievicz also joined James Connolly's socialist Irish Citizen Army (ICA), a small volunteer force formed in response to the lock-out of 1913, to defend the demonstrating workers from the police. Markievicz recruited volunteers to peel potatoes in a basement while she and others worked on distributing the food. As all the food was paid out of her own pocket, Markievicz was forced to take out many loans, at this time, and sold all her jewellery. That same year, with Inghinidhe na hÉireann, she ran a soup kitchen to feed poor school children.
Fashion advice attributed to her was: "Dress suitably in short skirts and strong boots, leave your jewels in the bank and buy a revolver."
In 1913 Markievicz's husband moved back to Ukraine, and never returned to live in Ireland. However, they did correspond and he was by her side when she died in 1927. As a member of the ICA, Markievicz took part in the 1916 Easter Rising. She was deeply inspired by the founder of the ICA, James Connolly. Markievicz designed the Citizen Army uniform and composed its anthem, based on the tune of a Polish song.
In the Rising, Markievicz fought in St Stephen's Green, where on the first morning—according to one account—she shot a member of the (unarmed) Dublin Metropolitan Police, who subsequently died of his injuries. Other accounts place her at City Hall when the policeman was shot, only arriving at Stephen's Green later. It was long thought that she was second in command to Michael Mallin, but in fact it was Christopher "Kit" Poole who held that position. Markievicz supervised the setting-up of barricades on Easter Monday and was in the middle of the fighting all around Stephen's Green, wounding a British army sniper. Trenches were dug in the Green, sheltered by the front gate; however, after British machine gun and rifle fire from the rooftops of tall buildings on the north side of the Green including the Shelbourne Hotel, the Citizen Army troops withdrew to the Royal College of Surgeons on the west side of the Green.
The Stephen's Green garrison held out for six days, ending the engagement when the British brought them a copy of Pearse's surrender order. The English officer, Captain (later Major) de Courcy Wheeler, who accepted their surrender was married to Markievicz's first cousin.
They were taken to Dublin Castle and Markievicz was transported to Kilmainham Gaol. They were jeered by the crowds as they walked through the streets of Dublin. There, she was the only one of 70 women prisoners who was put into solitary confinement. At her court martial on 4 May 1916, Markievicz pleaded not guilty to "taking part in an armed rebellion...for the purpose of assisting the enemy," but pleaded guilty to having attempted "to cause disaffection among the civil population of His Majesty". Markievicz told the court, "I went out to fight for Ireland's freedom and it does not matter what happens to me. I did what I thought was right and I stand by it." She was sentenced to death, but the court recommended mercy "solely and only on account of her sex". The sentence was commuted to life in prison. When told of this, she said to her captors, "I do wish your lot had the decency to shoot me".
Markievicz was transferred to Mountjoy Prison and then to Aylesbury Prison in England in July 1916. She was released from prison in 1917, along with others involved in the Rising, as the government in London granted a general amnesty for those who had participated in it. It was around this time that Markievicz, born into the Church of Ireland, converted to Catholicism.
In October 1919 Markievicz was imprisoned at Cork Gaol for making a seditious speech. At the 1918 general election, Markievicz was elected for the constituency of Dublin St Patrick's, beating her opponent William Field with 66% of the vote, as one of 73 Sinn Féin MPs. This made her the first woman elected to the British House of Commons. However, in line with Sinn Féin abstentionist policy, she would not take her seat in the House of Commons.
Markievicz was in Holloway prison, when her colleagues assembled in Dublin at the first meeting of the First Dáil, the Parliament of the revolutionary Irish Republic. When her name was called, she was described, like many of those elected, as being "imprisoned by the foreign enemy" (fé ghlas ag Gallaibh). She was re-elected to the Second Dáil in the elections of 1921.
Markievicz served as Minister for Labour from April 1919 to January 1922, in the Second Ministry and the Third Ministry of the Dáil. Holding cabinet rank from April to August 1919, she became both the first Irish female Cabinet Minister and at the same time, only the second female government minister in Europe. She was the only female cabinet minister in Irish history until 1979 when Máire Geoghegan-Quinn was appointed to the cabinet post of Minister for the Gaeltacht for Fianna Fáil.
Markievicz left government in January 1922 along with Éamon de Valera and others in opposition to the Anglo-Irish Treaty. She fought actively for the Republican cause in the Irish Civil War helping to defend Moran's Hotel in Dublin. After the War she toured the United States. She was not elected in the 1922 Irish general election but was returned in the 1923 general election for the Dublin South constituency. In common with other Republican candidates, she did not take her seat. However, her staunch republican views led her to being sent to jail again. In prison, she and 92 other female prisoners went on hunger strike. Within a month, she was released.
She joined Fianna Fáil on its foundation in 1926, chairing the inaugural meeting of the new party in La Scala Theatre. In the June 1927 general election, she was re-elected to the 5th Dáil as a candidate for the new Fianna Fáil party, which was pledged to return to Dáil Éireann, but died only five weeks later, before she could take up her seat.
Markievicz died at the age of 59 on 15 July 1927, of complications related to appendicitis. She had given away the last of her wealth, and died in a public ward "among the poor where she wanted to be". One of the doctors attending her was her revolutionary colleague, Kathleen Lynn. Also at her bedside were Casimir and Stanislas Markievicz, Éamon de Valera and Hanna Sheehy-Skeffington. Refused a state funeral by the Free State government, she was buried at Glasnevin Cemetery, Dublin, and de Valera gave the funeral oration.
Seán O'Casey said of her: "One thing she had in abundance—physical courage; with that she was clothed as with a garment."