Sir Denis Stanislaus Henry, 1st Baronet KBE, QC (7 March 1864 – 1 October 1925), was a British-Irish lawyer and politician who became the first Lord Chief Justice of Northern Ireland.
Henry was born in Cahore, Draperstown, County Londonderry, the son of prosperous Roman Catholic businessman. He was educated at Marist College, Dundalk; Mount St Mary's College, Chesterfield, a Jesuit foundation; and Queen's College, Belfast (QUB), where he won every law scholarship open to a student and many other prizes and exhibitions. In 1885, he was called to the Irish Bar.
During the general election campaign of 1895 Henry spoke in support of unionist candidates in two constituencies: Thomas Lea in South Londonderry, Henry's native constituency, and E T Herdman in East Donegal.
Henry's legal career flourished - he became a Queen's Counsel in 1896, a Bencher of the King's Inns in 1898 and ultimately Father of the Northwest Circuit - but his interest in politics did not diminish. By March 1905 he was a delegate at the inaugural meeting of the Ulster Unionist Council and the Unionist parliamentary candidate for the ultra-marginal North Tyrone seat.
On 23 May 1916, in the first by-election to be held in Ireland after the Easter rebellion, he was elected MP for South Londonderry. The rebellion had had no discernible impact on the contest at all.
In November 1918, he became Solicitor-General for Ireland and in July 1919 Attorney General for Ireland. He later served as the first Lord Chief Justice of Northern Ireland from 1921 to 1925. In 1923 he was created a Baronet, of Cahore in the County of Londonderry. He died in 1925, aged 61, and was buried near his native Draperstown.