John FitzGerald, de facto 12th Earl of Desmond

John FitzGerald, de facto 12th Earl of Desmond (d. 1536) was the brother of Thomas FitzGerald, 11th Earl of Desmond. Upon his brother's death in 1534, John disputed the title to the earldom of his brother's grandson, James FitzGerald, de jure 12th Earl of Desmond. John died in 1536. His grandnephew, the de jure earl, died in 1540, and was succeeded by John's son, James FitzGerald, 14th Earl of Desmond.

Alfred Webb tells us of this earl that he, "being supported by a large faction, was de facto [12th] Earl. This Sir John died about Christmas 1536."