Ussher, John (1524–1585?), merchant and mayor of Dublin, was the son of Christopher Ussher and his wife, Alison, daughter of Thomas Fitzwilliams, of Merrion, who after her first husband's death married James Fitzsimon and then Alderman James Sedgrave. Ussher had livery of his estate on 1 March 1545, paying a fine of 20 marks. In 1557 he served as part of an armed band of Dublin citizens in a royal campaign against the Scots in Ulster. In 1564 he was described as being a committed protestant, thereby gaining the approbation of leading royal officials. A merchant, he was sheriff of Dublin in 1555–6 and served as alderman of the city from 1562. He was mayor in 1574–5, twice acted as treasurer (1565–6 and 1577–8), and was chamberlain in 1581–2. During 1568–72 he frequently acted as courier for official correspondence between Dublin and London.
Ussher took advantage of his access to government ministers by proposing a scheme whereby he would receive a royal monopoly on the export of tanned leather hides from Ireland. The profits earned by the monopoly were to be used to endow a university in Dublin for the education of protestant clergy. Although the proposal had official backing and was considered during the 1569–71 Irish parliament, it foundered owing to the vigorous opposition of the merchant staplers of the Irish towns. Ussher's attempt to wrest the leather hide monopoly from the staplers infuriated his colleagues in the Dublin corporation to such an extent that he was temporarily removed as alderman between January and October 1573. However, his fellow aldermen recognised that his contacts in official circles in Dublin and London made him an effective spokesman for the city and he was restored to office. In 1577 he went to London on behalf of the Trinity Guild, securing a royal charter for it, and in 1581–2 spent a considerable time in London on behalf of Dublin city.
Ussher demonstrated his commitment to the spread of the protestant religion by funding the printing in Dublin in 1571 of a protestant catechism written in Irish by John Kearney (qv) (Seán Ó Cearnaigh), which included a brief introduction to the spelling and sound of the Irish language. It was called Aibidil Gaoidheilge, & caiticiosma. It was not, as has been asserted, the first printed book in the Irish language (a book in Irish was printed in Edinburgh in 1567), but it was the first known Irish-language catechism. In 1574 he wrote in Latin a religious tract, ‘De reformatione Hiberniae’, which was eventually deposited in Trinity College library. In 1577 he was appointed to a commission for ecclesiastical causes.
Ussher was a merchant with diverse commercial interests. In July 1582 he gave up his rights to a copper mine at Cashel. His residence was located on Bridgefoot Street, Dublin. In July 1573 he received a twenty-one-year lease on a number of properties, including a house with a wine cellar on Winetavern Street, which had formerly belonged to the abbey of St Thomas the Martyr, and a house at Wood Quay. He married Alice, daughter of alderman William Newman, former mayor of Dublin, with whom he had two sons, Christopher, who died while young, and Sir William (1563–1659), who married first Isabella (d. 1597), daughter of Adam Loftus (qv), Church of Ireland archbishop of Dublin, and second Margaret, daughter of Edward Cludde, of Shropshire. John Ussher, who played an important role in the political, commercial, and religious life of his city and country, probably died in 1585.