John FitzThomas, 1st Baron Desmond

John FitzThomas, 1st Baron Desmond (died 1261), was a Norman-Irish magnate and head of the Desmond line of the FitzGerald dynasty, the son of Thomas FitzMaurice. In 1259 he received a royal grant of Desmond and west Waterford, provoking Fineen MacCarthy, King of Desmond, who gathered the Gaelic clans against him.

At the Battle of Callann in July 1261 the Gaelic army routed the Normans, and John was killed together with his son Maurice FitzJohn. His infant grandson Thomas inherited the barony.