| Honorific-Prefix: | The Honourable |
| Leighton Goldie McCarthy | |
| Smallimage: | Leighton McCarthy.jpg |
| Office: | Ambassador of Canada to the United States |
| Term Start: | 24 February 1941 |
| Term End: | 31 December 1944 |
| Primeminister: | W. L. Mackenzie King |
| Predecessor: | Loring Christie |
| Successor: | Lester B. Pearson |
| Riding1: | Simcoe North |
| Parliament1: | Canadian |
| Predecessor1: | Dalton McCarthy |
| Successor1: | John Allister Currie |
| Term Start1: | 14 December 1898 |
| Term End1: | 21 September 1911 |
| Birth Date: | 15 December 1869 |
| Birth Place: | Walkerton, Ontario, Canada |
| Death Place: | Toronto, Ontario, Canada |
| Nationality: | Canadian |
| Party: | Independent (1898–1911) Liberal (1911–?) |
| Relations: | Dalton McCarthy (uncle) |
Leighton Goldie McCarthy (15 December 1869 - 3 October 1952) was a Canadian lawyer, politician, businessman and diplomat.
Born in Walkerton, Ontario, McCarthy was called to the Ontario Bar in 1892.[1] He was elected to the House of Commons of Canada in 1898 as an independent representing the riding of Simcoe North, following the death of the incumbent, his father Dalton McCarthy, in a carriage accident. He was re-elected in 1900 and 1904 but was defeated in 1911, when he ran as a Liberal.
In 1928, McCarthy became president of the Canada Life Assurance Company.[2] In 1941, he was appointed to the Queen's Privy Council for Canada.
From 1941 to 1944, McCarthy served as Canada's top diplomatic representative in Washington, D.C., and he became the first Canadian ambassador to the United States (previously, the position was called Envoy Extraordinary and Minister Plenipotentiary). McCarthy was a lawyer before and after his political and diplomatic appointment but ended his practice in 1946.
McCarthy moved to Toronto and built a house at 45 Walmer Road in 1932,[3] and he died here in 1952. McCarthy bequeathed his home to the University of Toronto.[4] Since 1953, the building has housed the university's Institute of Child Study.
There is a Leighton G. McCarthy and family fonds at Library and Archives Canada.[5] Archival reference number is R4172.