The Irish Volunteers (Irish: Óglaigh na hÉireann), also known as the Irish Volunteer Force or the Irish Volunteer Army, was a paramilitary organisation established in 1913 by nationalists and republicans in Ireland. It was ostensibly formed in response to the formation of its Irish unionist/loyalist counterpart the Ulster Volunteers in 1912, and its declared primary aim was "to secure and maintain the rights and liberties common to the whole people of Ireland". Its ranks included members of the Conradh na Gaeilge (Gaelic League), Ancient Order of Hibernians, Sinn Féin and the Irish Republican Brotherhood. Increasing rapidly to a strength of nearly 200,000 by mid-1914, it split in September of that year over John Redmond's support for the British war effort during World War I, with the smaller group opposed to Redmond's decision retaining the name Irish Volunteers.

The Irish Home Rule movement dominated political debate in the British Isles since Prime Minister William Ewart Gladstone introduced the first Home Rule Bill in 1886, intended to grant a measure of self-government and national autonomy to Ireland, but which was rejected by the House of Commons of the United Kingdom. The second Home Rule Bill, seven years later having passed the House of Commons, was vetoed by the House of Lords. It would be the third Home Rule Bill, introduced in 1912, which would lead to the crisis in Ireland between the Irish Catholics, most of whom were nationalists, and Unionists in Ulster.

On 28 September 1912 at Belfast City Hall just over 450,000 Unionists signed the Ulster Covenant to resist the granting of Home Rule. This was followed in January 1913 with the formation of the Ulster Volunteers composed of adult male Unionists to oppose the passage and implementation of the bill by force of arms if necessary. Nationalist politician Eoin MacNeill claimed that the establishment of the Ulster Volunteers was instigated, approved, and financed by members of Conservative Party; MacNeill further claimed that the Liberal Party was not "terribly distressed by that proceeding."

The initiative for a series of meetings leading up to the public inauguration of the Irish Volunteers came from the Irish Republican Brotherhood (IRB). Bulmer Hobson, co-founder of the republican boy scouts, Fianna Éireann, and member of the Irish Republican Brotherhood, believed the IRB should use the formation of the Ulster Volunteers as an "excuse to try to persuade the public to form an Irish volunteer force". The IRB could not move in the direction of a volunteer force themselves, as any such action by known proponents of physical force would be suppressed, despite the precedent established by the Ulster Volunteers. They therefore confined themselves to encouraging the view that nationalists also ought to organise a volunteer force for the defence of Ireland. A small committee then began to meet regularly in Dublin from July 1913, who watched the growth of this opinion. They refrained however from any action until the precedent of Ulster should have first been established while waiting for the lead to come from a "constitutional" quarter.

The IRB began the preparations for the open organisation of the Irish Volunteers in January 1913. James Stritch, an IRB member, had the Irish National Foresters build a hall at the back of 41 Parnell Square in Dublin, which was the headquarters of the Wolfe Tone Clubs. Anticipating the formation of the Volunteers they began to learn foot-drill and military movements. The drilling was conducted by Stritch together with members of Fianna Éireann. They began by drilling a small number of IRB associated with the Dublin Gaelic Athletic Association, led by Harry Boland.

Michael Collins along with several other IRB members claim that the formation of the Irish Volunteers was not merely a "knee-jerk reaction" to the Ulster Volunteers, which is often supposed, but was in fact the "old Irish Republican Brotherhood in fuller force."

The IRB knew they would need a highly regarded figure as a public front that would conceal the reality of their control. The IRB found in Eoin MacNeill, Professor of Early and Medieval History at University College Dublin, the ideal candidate. McNeill's academic credentials and reputation for integrity and political moderation had widespread appeal.

The O'Rahilly, assistant editor and circulation manager of the Gaelic League newspaper An Claidheamh Soluis, encouraged MacNeill to write an article for the first issue of a new series of articles for the paper. The O'Rahilly suggested to MacNeill that it should be on some wider subject than mere Gaelic pursuits. It was this suggestion which gave rise to the article entitled The North Began, giving the Irish Volunteers its public origins. On 1 November, MacNeill's article suggesting the formation of an Irish volunteer force was published. MacNeill wrote,