| Thomas Edgar Lacy | |
| Birth Date: | 7 February 1804[1] |
| Death Date: | 22 February 1880[2] |
| Birth Place: | London, England |
| Death Place: | Middlesex, England |
| Allegiance: |  United Kingdom |
| Rank: | Lieutenant-General |
Lieutenant-General Thomas Edgar Lacy (7 February 1804 – 22 February 1880) was a British Army officer who became Commandant, Staff College, Sandhurst.
Lacy was commissioned into the 72nd Highlanders in 1826.[3] He was promoted to lieutenant on 3 October 1826, to captain on 11 July 1834 and to major on 10 November 1846. He became Town Major of Gibraltar on 13 August 1847. He was promoted to lieutenant-colonel on 22 June 1854.
He became Commandant, Staff College, Sandhurst on 1 January 1865. He was promoted to lieutenant-general on his retirement in October 1877.