The All-for-Ireland League (AFIL) was an Irish, Munster-based political party (1909–1918). Founded by William O'Brien MP, it generated a new national movement to achieve agreement between the different parties concerned on the historically difficult aim of Home Rule for the whole of Ireland. The AFIL established itself as a separate non-sectarian party in the House of Commons of the United Kingdom of Great Britain and Ireland, binding a group of independent nationalists MPs to pursue a broader concept of Irish nationalism, a consensus of political brotherhood and reconciliation among all Irishmen, primarily to win Unionist consent to an All-Ireland parliamentary settlement.

O'Brien's conciliatory initiation of the 1902 Land Conference, achieved with the backing of the United Irish League (UIL) which he had founded, led to agreement on the Land Purchase (Ireland) Act 1903, which resolved Ireland's century old land question. This was followed by the housing of agricultural labourers, settled under the Labourers (Ireland) Act 1906. With Irish local government already well established, O'Brien was convinced that to achieve the final hurdle of All-Ireland self-government, the success of the approach he used to win the Land Act, the "doctrine of conciliation" combined with "conference plus business", must also be applied to alleviate the fears and integrate the interests of the Protestant and Unionist community in their resistance to Irish Home Rule since 1886. The issue was a source of contention amongst a significant majority of Unionists (largely but not exclusively based in Ulster), who opposed Home Rule, fearing that a Catholic Nationalist ("Rome Rule") Parliament in Dublin would discriminate or retaliate against them, impose Roman Catholic doctrine, and impose tariffs on industry. While most of Ireland was primarily agricultural, six of the counties in Ulster were the location of heavy industry and would be affected by any tariff barriers imposed.

Following the success with the Land Purchase Act, the Irish Parliamentary Party (IPP) was long disrupted by internal dissensions after it had alienated William O'Brien from the party in November 1903. He was condemned by party leader John Dillon for allegedly making former tenant farmers less dependent on the party and for the manner in which he secured a new political base in Munster through his alliance with D. D. Sheehan and the Irish Land and Labour Association. In addition, forging further alliances with T. M. Healy and unionist devolutionists during 1904–05 in his engagement with the Irish Reform Association and ensuing support for the Irish Council Bill. By 1907 the country called for reunion of the split party ranks and in November O'Brien's proposals for his and other Independent's return to the Party were accepted. Their return to the Nationalist fold in mid-January 1908 was however to be short-lived, as conflict ensued from the government's intention to amend the Land Act 1903.

O'Brien had always been gravely disturbed by the Irish Parliamentary Party's involvement with "that sinister sectarian secret society", the Ancient Order of Hibernians (AOH) also known as the Molly Maguires, or the Mollies – what he called "the most damnable fact in the history of this country", and was bitterly resentful and unsparing in his attacks upon it. AOH members represented deeply sectarian pseudo Gaelic-Catholic-nationalism of a Ribbon tradition, their Ulster Protestant counterpart the Orange Order. The AOH Grandmaster was a young Belfast man of remarkable political ability, Joseph Devlin MP, who attached himself to the Dillonite section of the Irish Party, as well as being General Secretary of its adopted United Irish League (UIL). Devlin was already known as "the real Chief Secretary of Ireland", his AOH spreading successfully and eventually saturating the entire island. Even in Dublin the AOH could draw large crowds and stage impressive demonstrations. In 1907, Devlin was able to assure John Redmond, the Irish Party leader, that a planned meeting of the UIL would be well attended because he would be able to get more than 400 AOH delegates to fill the hall.

As prelude to O'Brien's formation of the AFIL, Redmond called a National Convention at the Mansion House, Dublin, 9 February 1909, to win support for a House of Commons bill introducing compulsory land purchase while curtailing funding of tenant land purchase under the Birrell Land Act (1909). Over 3000 UIL delegates attended. Redmond, who chaired the meeting, claimed it would burden the British Treasury and local ratepayers excessively. O'Brien argued that the curtailing Bill would kill land purchase by provoking refusal by landlords to sell and worsen relations between tenants and landlords. The convention was obviously loaded against O'Brien when delegates suspected of supporting him were excluded at the entrance and assaulted in "probably the stormiest meeting ever held by constitutional nationalists".

When he attempted to speak O'Brien was howled down by various contingents of Belfast Hibernians and midland cattle-drivers, their presence pre-organised by Devlin's AOH organisation. Its stewards, armed with batons, attacked O'Brien's follower who had gained entrance, their general order to "Let no one with a 'Cork accent' get near the platform". From which the event earned the name Baton Convention. When Eugene Crean MP for South East Cork was attacked on the platform, it developed into a mêlée with Devlin and his lodgemen, after D. D. Sheehan and James Gilhooly, MP for West Cork, intervened against Crean's assailants, this in Redmond's presence. Others targeted were members of the Young Ireland Branch, Frank Cruise O'Brien and Francis Sheehy-Skeffington, who called Devlin a brainless bludgeoner.

Regarding himself as having been driven from the party by Hibernian hooligans, O'Brien's subsequent move was to officially constitute his new movement, the "All-for-Ireland League", its embryonic origins – the successful Land Conference of 1902, which he launched at a public rally in Kanturk in March 1909. It was immediately openly denounced by Redmond, and at an Irish party meeting held on 23 March, the party voted fifty to one that membership in the League was incompatible with party membership. O'Brien suffered a health breakdown in April, and retired from politics to Italy to recuperate. Control of the fledgling AFIL passed to a Provisional Committee led by D. D. Sheehan (MP) as Honorary Secretary, its foremost task to promote the League's principles and to hold O'Brien's seat in Cork at the inevitable by-election until his return.

From Italy O'Brien looked to an alliance with Arthur Griffith's moderate Sinn Féin movement through emissaries James Brady (a Dublin solicitor), John Shawe-Taylor and Tim Healy. O'Brien offered funds for Sinn Féin candidates to run in Dublin and funds to run its paper Sinn Féin, in return for Sinn Féin support of his candidates in the south. A special Sinn Feín executive council meeting called 20 December 1909 seriously considered these overtures, many present in favour of co-operation. Sinn Féin's William Sears reported the result: "Regret cannot cooperate because the Constitution will not allow us. Mr. Griffith was in favour of cooperation if possible". Nevertheless, in the following years O'Brien and his party continued to associate itself with Griffith's movement both in and out of Parliament. In June 1918, Griffith asked O'Brien to have the writ moved for his candidacy in the East Cavan by-election (moved by AFIL MP Eugene Crean) when Griffith was elected with a sizeable majority.