| Honorific-Prefix: | The Right Honourable |
| The Lord Acton | |
| Office: | Member of the House of Lords Lord Temporal |
| Term Start: | 15 December 1928 |
| Term End: | 23 January 1989 Hereditary Peerage |
| Predecessor: | The 2nd Lord Acton |
| Successor: | The 4th Lord Acton |
| Birth Date: | 15 December 1907 |
| Birth Place: | Bordighera, Liguria, Italy |
| Death Date: | 23 January 1989 |
| Death Place: | Mallorca, Spain |
| Spouse: | Daphne Strutt |
| Children: | 11 |
| Father: | Richard Lyon-Dalberg-Acton, 2nd Baron Acton |
| Nationality: | British |
| Alma Mater: | Royal Military College, Sandhurst Trinity College, Cambridge |
John Emerich Henry Lyon-Dalberg-Acton, 3rd Baron Acton (born Dalberg-Acton; 15 December 1907 – 23 January 1989), was a British peer and soldier.
Acton was born in Bordighera, Liguria, Italy,[1] the eldest son and third of nine children born to Richard Dalberg-Acton, 2nd Baron Acton, a diplomat in the foreign service. His mother was Dorothy Lyon, the only child of Thomas Henry Lyon, DL, of Appleton Hall, Cheshire.[2] The fourth generation of his family abroad, the 2nd Lord Acton and his children officially became British citizens in 1911 by Act of Parliament.[3]
The family was living in Germany when the First World War broke out. They were temporarily detained in Baden Baden in 1914. In 1915, Lord Acton became chargé d'affaires in Bern. In 1919, his father added the additional surname and arms of Lyon when Lady Acton inherited from her father.[2] His mother died in 1923, when his youngest sister was just 2.[4]
He was educated at the Royal Military College, Sandhurst and Trinity College, Cambridge. He succeeded to the family titles upon the death of his father in 1924.[2]
His only brother, Richard William Heribert Peter Lyon-Dalberg-Acton (1909–1946), was killed in a plane crash in Gambia in 1946.[2]
In December 1945, Acton was appointed to the Military Division of the Order of the British Empire as a Member. In February 1947, he was appointed to be a Deputy Lieutenant of the County of Salop but resigned his commission in November the same year because he stopped living in the county. In the 1964 New Year Honours, Acton was appointed to the Order of St Michael and St George as a Companion.
Acton was a devout Catholic.[5] He was a founder and president of the multiracial National Club in Salisbury, Rhodesia.
He married Daphne Strutt (d. 2003), daughter of The 4th Baron Rayleigh, on 25 November 1931. The couple had eleven children:
He died in Mallorca, Spain in 1989.[6]