Geoffrey of St. John (died 1258) was an English-born clergyman who became Bishop of Ferns.
He came to Ireland in the entourage of his predecessor as Bishop, John of St John, who is thought to have been his brother.
Geoffrey became Treasurer of Limerick Cathedral, and was presented to the living of Carrickfergus in 1224.
Like his predecessor he served as Chief Escheator of Ireland, being appointed in 1250, and as a justice in eyre from 1252, becoming senior justice in 1255.
On the death of Bishop John, which probably occurred in 1253, Geoffrey was elected to succeed him in 1254.