| Honorific-Prefix: | Major General |
| Sir Terence O'Brien | |
| Order: | Acting |
| Office: | Governor of British Ceylon |
| Term Start: | 1 December 1863 |
| Term End: | 21 March 1865 |
| Predecessor: | Charles Justin MacCarthy |
| Successor: | Hercules Robinson |
| Order2: | 22nd |
| Office2: | General Officer Commanding, Ceylon |
| Term Start2: | 1860 |
| Term End2: | ? |
| Predecessor2: | Henry Frederick Lockyer |
| Successor2: | Studholme John Hodson |
| Birth Date: | 23 April 1830 |
| Birth Place: | Manchester, Lancashire, England |
| Death Place: | London, England |
| Birthname: | John Terence Nicholls O'Brien |
| Allegiance: | United Kingdom |
| Branch: | British Army |
| Rank: | Major general |
| Commands: | General Officer Commanding, Ceylon |
Major General Sir John Terence Nicholls O'Brien (23 April 1830 – 25 February 1903[1]) was a surveyor, engineer and colonial governor.
Born in Manchester, England, O'Brien studied at Elizabeth College, Guernsey, and then attended the Royal Military College, Sandhurst.
O'Brien, a British Army officer, received a medal of honour for his service in the Indian Mutiny War. He was appointed acting Governor of British Ceylon in 1863 and held the office for two years, succeeding Charles Justin MacCarthy.[2]
In 1881, he was appointed governor of Heligoland, knighted in 1888 and became governor of Newfoundland in 1889.
O'Brien as governor of Newfoundland helped precipitate the 1894 bank crash by his many dispatches to London noting that Newfoundland politicians under Premier William Whiteway's Liberal Government were uniquely corrupt and incompetent. He resigned from office in 1895 and returned to London.
The Newfoundland community of Terenceville was so named in his honour. O'Brien's son, Sir Charles O'Brien, also became a colonial governor.
O'Brien died in 1903 in London, England.