Conradh na Gaeilge is founded by Douglas Hyde, the son of a Church of Ireland rector from Frenchpark, County Roscommon, with the aid of Eugene O’Growney, Eoin MacNeill, Thomas O’Neill Russell, and others. The organisation develops from Ulick Bourke‘s earlier Gaelic Union and becomes the leading institution promoting the Gaelic Revival, carrying on efforts like the publishing of the Gaelic Journal. The League’s first newspaper is An Claidheamh Soluis (The Sword of Light) and its most noted editor is Patrick Pearse. The motto of the League is Sinn Féin, Sinn Féin amháin (Ourselves, Ourselves alone).
The League encourages female participation from the start and a number of women play a prominent role. They are not restricted to subordinate roles, but play an active part in leadership, although males are in the overwhelming majority. Local notables, such as Lady Gregory in Galway, Lady Esmonde in County Wexford, and Mary Spring Rice in County Limerick, and others such as Norma Borthwick, found and lead branches in their communities. At the annual national convention in 1906 women are elected to seven of the forty-five positions on the Gaelic League executive. Executive members include Máire Ní Chinnéide, Úna Ní Fhaircheallaigh (who writes pamphlets on behalf of the League), Bean an Doc Uí Choisdealbha, Máire Ní hAodáin, Máire de Buitléir, Nellie O’Brien, Eibhlín Ní Dhonnabháin, and Eibhlín Nic Néill.
Though apolitical, the organisation attracts many Irish nationalists of different persuasions, much like the Gaelic Athletic Association. It is through the League that many future political leaders and rebels first meet, laying the foundation for groups such as the Irish Volunteers. However, Conradh na Gaeilge does not commit itself entirely to the national movement until 1915, causing the resignation of Douglas Hyde, who feels that the culture of language should be above politics. Most of the signatories of the 1916 Proclamation are members. It still continues to attract many Irish Republicans. Seán Mac Stíofáin, the first chief of staff of the Provisional IRA was a prominent member in his later life.
After the foundation of the Irish Free State in 1922, the organisation has a less prominent role in public life as Irish is made a compulsory subject in state-funded schools. It does unexpectedly bad in the Irish Seanad election of 1925, when all the candidates it endorses are defeated, including Hyde.