Sir Henry Echlin, 1st Baronet (1652–1725) was an Irish barrister, judge, and bibliophile. He was the first of the Echlin Baronets of Clonagh, County Kildare.
He was born at Ardquin, County Down, the second son of Robert Echlin and great-grandson of Robert Echlin, who was Bishop of Down and Connor from 1612 to 1635. His mother was Mary Leslie, daughter of Henry Leslie, Bishop of Meath (died 1661) and his wife Jane Swinton. His father died when his children were still very young, and seems to have left his family in some financial difficulty. Henry's younger brother was Lieutenant-General Robert Echlin (c.1657-c.1723), commander of the 6th (Inniskilling) Dragoons, and later a prominent Jacobite.
He gained useful experience by working in the courts as a clerk while still in his teens, no doubt to supplement his income, and at the same time attended the University of Dublin; he matriculated in 1667, was Scholar in 1668, and became Master of Arts in 1703. He practiced for some time as an attorney, then entered Lincoln's Inn in 1672 and the King's Inns in 1677.
In 1683, he was appointed Third Serjeant-at-law. Since he was barely thirty and had only been in practice at the Irish Bar for six years, his appointment caused some surprise. Like almost all legal appointments at the time, it was largely due to the influence of James Butler, 1st Duke of Ormonde, the Lord Lieutenant of Ireland; Echlin also had the support of Sir John Temple, the Solicitor General for Ireland, who justified the appointment as follows: