governor, was born on 21 December 1827, the fourth son of Mathias Callaghan of Midleton, Co Cork and Charlotte Fitzgerald. He studied at Trinity College Dublin and at Lincoln's Inn in London. He held the appointment of Barrington lecturer on Political Economy to the Dublin Statistical Society, was called to the Irish Bar in 1854 and was counsel to the attorney general for Ireland.

He was appointed chief magistrate in Hong Kong in 1860 and began a career in colonial administration. From 1861-1867 he was governor of Labuan and consul general for Borneo. In 1871 he was administrator of the government of the Gambia.

He was appointed governor of the Falkland Islands in 1876 with a salary of £1,200 plus fees.

Callaghan arrived in May 1876 succeeding the disorganised Governor D'ARCY: 'poor D'Arcy ought not to be regarded as a responsible being in matters of business,' he noted. The colony had liabilities of £3,973. He proved an efficient governor and an official in London minuted: 'I think that Mr Callaghan deserves praise for the trouble and success with which he has dealt with this subject'.

Like many governors, he was concerned by the power of the Falkland Islands Company. Writing in London (where he had returned in 1878 after his mother's death) he told the Colonial Office:

I can assure you that I have been no "Company-phobe" and since I have been here have done all I could to oblige them and Mr [John Markham] DEAN, but their demands from time to time have been most unreasonable. These two interests will before long become a formidable and troublesome power to the government if some effort is not made to bring them to their proper bearings.

The following year he wrote a confidential despatch giving an interesting account of the power of monopolists [FIC & Dean] in the colony and the detrimental effect they had on colonists' wish to save money. Their mails contract had reinforced the power of the FIC. 'If the present state of things is allowed to continue the colony will never progress nor prosper'. Callaghan was disturbed that on his leave BAILEY, who had been left in charge, 'from his long residence here has become too subject to local influences to be able to withstand the strong pressure put upon him [by the land-owners]'. He believed that FE COBB was guilty of sharp practice in inducing Bailey to grant land to the FIC in 1879 just before Callaghan himself returned from leave.

In July 1879, Callaghan asked for a transfer on account of his wife's health.

In 1880 he became governor of the Bahamas and was still in service when he died in New York on 8 July 1881.

A road in Stanley is named after him.