| Honorific Prefix: | His Excellency |
| Terence Daniel O'Leary | |
| Office: | Governor of Pitcairn |
| Primeminister: | Margaret Thatcher |
| Term Start: | 1984 |
| Term End: | 1988 |
| Predecessor: | Richard Stratton |
| Successor: | Robin Byatt |
| Office2: | British High Commissioner to New Zealand and Samoa |
| Monarch2: | Elizabeth II |
| Primeminister2: | Margaret Thatcher |
| Term Start2: | 1984 |
| Term End2: | 1988 |
| Predecessor2: | Richard Stratton |
| Successor2: | Robin Byatt |
| Office3: | British High Commissioner to Sierra Leone |
| Monarch3: | Elizabeth II |
| Primeminister3: | Margaret Thatcher |
| Term Start3: | 1981 |
| Term End3: | 1984 |
| Predecessor3: | Michael Hugh Moran |
| Successor3: | Richard Clift |
| Birth Date: | 18 August 1928 |
| Nationality: | British |
| Occupation: | Diplomat |
Terence Daniel O'Leary CMG (18 August 1928 – 11 July 2006)[1] was a British diplomat. He served as High Commissioner to Sierra Leone from 1981 to 1984 and High Commissioner to New Zealand from 1984 to 1988. While High Commissioner to New Zealand, he also served as Governor of Pitcairn.
O'Leary was educated at Dulwich College and St John's College, Cambridge, where he studied history.[1]
He worked in the Commonwealth Relations Office from 1953 to 1956.[2] He was second secretary at the High Commission to New Zealand in Wellington from May 1956 to March 1958, first secretary at the Commonwealth Relations Office in 1958, and first secretary in the High Commission to India in Delhi from 1960 to 1962. He worked at the High Commission to Tanganyika in Dar es Salaam from 1962 to 1963 and in the High Commission to Australia in Canberra from 1965 to 1968, when he returned to the Commonwealth Relations Office as first secretary.
He married Janet Douglas Berney in 1960.[2]