James Ussher (or Usher; 4 January 1581 – 21 March 1656) was the Church of Ireland Archbishop of Armagh and Primate of All Ireland between 1625 and 1656. He was a prolific Irish scholar and church leader, who today is most famous for his identification of the genuine letters of the church father, Ignatius of Antioch, and for his chronology that sought to establish the time and date of the creation as "the entrance of the night preceding the 23rd day of October ... the year before Christ 4004"; that is, around 6 pm on 22 October 4004 BC, per the proleptic Julian calendar.

Ussher was born in Dublin to a well-to-do family. His maternal grandfather, James Stanihurst, had been speaker of the Irish parliament. Ussher's father, Arland Ussher, was a clerk in chancery who married Stanihurst's daughter, Margaret (by his first wife Anne Fitzsimon), who was reportedly a Roman Catholic.

Ussher's younger and only surviving brother, Ambrose, became a distinguished scholar of Arabic and Hebrew. According to his chaplain and biographer, Nicholas Bernard, the elder brother was taught to read by two blind, spinster aunts. A gifted polyglot, he entered Dublin Free School and then the newly founded (1591) Trinity College Dublin on 9 January 1594, at the age of thirteen (not an unusual age at the time). He had received his Bachelor of Arts degree by 1598 and was a fellow and MA by 1600 (though Bernard claims he did not gain his MA till 1601). In May 1602, he was ordained in the Trinity College Chapel as a deacon in the Protestant, established, Church of Ireland (and possibly priest on the same day, while Martin Gorst says that he became a priest on 20 December 1601) by his uncle

Ussher went on to become Chancellor of St Patrick's Cathedral, Dublin in 1605 and Prebend of Finglas. He became Professor of Theological Controversies at Trinity College and a Bachelor of Divinity in 1607, Doctor of Divinity in 1612, and then Vice-Chancellor in 1615 and vice-provost in 1616. In 1613, he married Phoebe, daughter of a previous Vice-Provost, Luke Challoner, and published his first work. In 1615, he was closely involved with the drawing up of the first confession of faith of the Church of Ireland, the Irish Articles of Religion.

James was born in the parish of St. Nicholas, to Arland Ussher (1545–1598) and Margaret Ussher (née Stanihurst) (1547–1601). It is recorded in Alfred Webb's, A Compendium of Irish Biography (1878) that his father, a clerk in the court of Chancery, was said to have been descended from one, Neville, who came over (to Ireland) with King John in the capacity of usher and had changed his name to that of his office. James was taught to read by two aunts who had been blind from infancy, to whom he ever afterward looked back with affection and respect. From eight to thirteen years of age he attended the school kept by Fullerton and Hamilton, private emissaries of James VI of Scotland, sent to keep up his influence in Ireland, in view of the prospect of his succeeding to the throne of England and Ireland."

James's abilities, diligence, and loving disposition from youth are described as "attracting the esteem of all with whom he came in contact." He became one of the first and leading scholars of Trinity College, Dublin (opened 1593).

In the beginning of 1614 he married his cousin, Phoebe, daughter of his maternal uncle Dr Lucas Challanor. Webb tells how Phoebe had been enjoined by her father's will, bequeathing her a considerable property, not to marry any other than Dr. Usher, "should he propose himself." [1]

1619 Ussher travelled to England, where he remained for two years.