Thomas James Stanislaus Harbison (8 November 1864 – 22 November 1930) was an Irish nationalist politician.

He was born in Cookstown, County Tyrone, to John Harbison, a general merchant, and Isabella Daly.

Harbison studied at St Malachy's College in Belfast. He became active in the Irish Parliamentary Party, acting from 1906 until 1910 as the election agent for William Redmond and Tom Kettle. In 1911, he was elected to Tyrone County Council.

After attending the Irish Convention, he was elected to Westminster at the 1918 East Tyrone by-election, after Redmond resigned it to contest Waterford City. At the 1918 general election, Harbison was elected in North East Tyrone. Speaking the House of Parliament (11 November 1920) on the day that the Government of Ireland Act 1920 was passed Harbison made clear his feelings on the Act and the Partition of Ireland:

"This is not a Bill for the better government of Ireland. I believe that the people in the county that I represent would be legally justified in using every form of resistance in their power to prevent this Act, if it ever becomes an Act, from coming into operation. It is a sentence of death, in my opinion, upon us as a unit in that Parliament. Our liberties are gone; and if the younger men of Ireland become indignant, and take courses that no sane man could defend, who will be responsible? The responsibility will be upon the men who have produced this Bill at the dictates of a narrow-minded set of reactionaries in the North-East corner of Ulster. It is a very small corner of Ulster; I have the map of it here. A set of reactionaries in that corner will have us under their heel for all time. I know the feeling of the men whom I represent, and I assure you, on this Armistice night, when all should be peace, that you are going to create, not peace, but eternal dissatisfaction, division, and, I am afraid, destruction."

At the 1921 Northern Ireland general election, Harbison was elected on an abstentionist platform in Fermanagh and Tyrone. In 1922, he was elected in the Westminster constituency of Fermanagh and Tyrone along with Cahir Healy for the Nationalist Party. With majorities of more than 6,000 votes over the Unionist candidates, their elections were seen as a plebiscite on the issue of the Partition of Ireland. He stood down from the Westminster seat at the 1924 election, and in 1927 took his seat at Stormont. In 1929, he stood down from his Stormont seat, but was again elected to Westminster, serving until his death a year later.