James O'Mara (6 August 1873 – 21 November 1948) was an Irish businessman and politician who became a nationalist leader and key member of the revolutionary First Dáil. As an MP in the House of Commons of the United Kingdom, he introduced the bill which made Saint Patrick's Day a national holiday in Ireland in 1903. He was one of the few politicians to have served both as member in the House of Commons and in Dáil Éireann.
O'Mara was born in Limerick, son of Stephen O'Mara and Elen Pigott  and educated by the Christian Brothers in Limerick, and at Clongowes Wood College in Dublin. His studies at the Royal University of Ireland were postponed after the death of his Uncle Jim in 1893, when James was sent to London to take over his Uncle's business functions. After his marriage in 1895 to Agnes Cashel, sister of the republican activist in later life Alice Cashel, he moved to Epsom in Surrey, and then to Sydenham in London. He finally got his B.A. degree from the Royal University in 1898.
His career in Westminster is noted for his introduction of the Bill which became the Bank Holiday (Ireland) Act 1903, making Saint Patrick's Day a national holiday. O'Mara later introduced the law which required that pubs be closed on 17 March, a provision which was repealed only in the 1970s.
In 1907, O'Mara resigned from Parliament and from the Irish Parliamentary Party to join Sinn Féin, the first MP to do so. He returned to Dublin in 1914 to continue his work in the bacon business, and remained active in Sinn Féin.
At the 1918 general election, he was Sinn Féin's Director of Finance and the party's fourth Director of Elections (his three predecessors having been imprisoned). He was elected as a Sinn Féin MP for his old constituency of Kilkenny South, defeating the Irish Party's Matthew Keating by 8,685 votes to 1,855. South Kilkenny was one of 73 constituencies returning Sinn Féin MPs pledged not to take their seats at Westminster. In the First Dáil Éireann he became Trustee of Dáil Éireann funds, and travelled to the United States with Éamon de Valera to pursue a fund-raising drive. He resigned his trusteeship and his Dáil seat in 1921 after a disagreement with de Valera.
A supporter of the 1921 Anglo-Irish Treaty, he was appointed as the first Irish Ambassador to the United States, but served only briefly.
After the death in 1923 of Philip Cosgrave, the Cumann na nGaedheal TD for Dublin South and brother of W. T. Cosgrave, O'Mara stood as the Cumann na nGaedheal candidate in the resulting by-election. Polling took place on 12 March 1924, and O'Mara was returned to the 4th Dáil, which sat until 1927. He did not contest the June 1927 general election, and retired from politics.
- Down Memory Lane at the Wayback Machine (archived 4 November 1999) (Limerick Leader, Saturday, 12 December 1998)
- James O'Mara family tree
- Brian M. Walker (ed.), Parliamentary Election Results in Ireland, 1801-1922, Dublin, Royal Irish Academy, 1978
- Hansard 1803–2005: contributions in Parliament by James O'Mara
|Parliament of the United Kingdom|
(Irish Parliamentary Party)
| Sinn Féin MP for South Kilkenny
| Member of parliament for South Kilkenny
Nicholas Joseph Murphy
|New constituency|| Sinn Féin Teachta Dála for South Kilkenny
Cumann na nGaedheal)
| Cumann na nGaedheal Teachta Dála for Dublin South
Cumann na nGaedheal)