John de Courcy, 21st Baron Kingsale

John de Courcy, 21st Baron Kingsale (died 1667) sat in the House of Lords of the Irish Parliament of 1661–1666.

John was born the eldest son of Patrick de Courcy and Mary FitzGerald. His father was the 20th Baron Kingsale (also counted as the 19th or the 15th). His father's family, the de Courcys, were Old English and claimed descendence from John de Courcy, who had arrived in Ireland in 1176.

His mother was a daughter of John Oge FitzGerald of Dromana. Her eldest sister, Helen (or Ellen) was the wife of his uncle Gerald, the 19th Baron Kingsale. The FitzGeralds of Dromana were Old English like the de Courcys. They were a cadet branch of the FitzGeralds of Desmond that started when Gerald FitzGerald, the second son of James FitzGerald, 6th Earl of Desmond (d. 1462) was given Dromana as an appanage.

His parents married when his father was already 48 years old but had 23 children. However, only seven seem to be known by name.

His father was Baron Kingsale from about 1642 to 1663, during the 11 years of war that followed the Irish Rebellion of 1641, then through the eight years of Cromwellian rule in Ireland, and last through the Restoration.

De Courcy married Ellen, daughter of Charles MacCarthy Reagh of Kilbrittain and granddaughter of Donal MacCarthy Reagh of Kilbrittain.

John and Ellen had three sons:

1. Patrick (1660–1669), succeeded as the 22nd Baron
2. Almeric (1664–1720), succeeded as the 23rd Baron
3. William

—and at least one daughter:

1. Ellen, married Sir John Magrath, 3rd Baronet

John succeeded his father in 1663 as the 21st Baron Kingsale. He took his seat in the Irish House of Lords as Lord Kingsale on 9 November 1665.

Kingsale died of smallpox on 19 May 1667. He was succeeded by his eldest son Patrick aged seven.