Sir Anthony St Leger (c. 1496 – 16 March 1559; or Sellenger), KG, of Ulcombe and Leeds Castle in Kent, was an English politician and Lord Deputy of Ireland during the Tudor period.
Anthony St Leger was the eldest son of Ralph II St Leger of Ulcombe, Kent by his wife Isabel (or Elizabeth) Haute, daughter of Richard Haute (d. 8 April 1487) by his wife Elizabeth Tyrrell, widow of Sir Robert Darcy (c.1420 - 2 November 1469) of Maldon, Essex, and daughter of Sir Thomas Tyrrell (d. 28 March 1477) of Heron in the parish of East Horndon, Essex.
He was educated abroad and at the University of Cambridge. He quickly gained the favour of King Henry VIII (1509–1547), and in 1537 was appointed president of a commission of enquiry into the condition of Ireland. In the course of this work, he obtained much useful knowledge of the country. In 1539 he was knighted and appointed Sheriff of Kent.
On 7 July 1540, Sir Anthony was appointed Lord Deputy of Ireland and tasked with the repression of disorder. He moved against the MacMorrough Kavanagh clan, who had long claimed the title King of Leinster, permitting them to retain their lands only by accepting feudal tenure on the English model. By a similar policy he exacted obedience from the O'Mores, O'Tooles and O'Conors in Leix and Offaly. Having conciliated the O'Briens in the west and the Earl of Desmond in the south, he obtained the passage of an act in the Irish Parliament in Dublin which conferred the title of King of Ireland on King Henry VIII and his heirs. Conn O'Neill, who had remained sullenly hostile, was forced to submit.