Trevelyan is the son of a Cornish clergyman, the Venerable George Trevelyan, who becomes Archdeacon of Taunton, and his wife Harriet, daughter of Sir Richard Neave. As a young man, he works with the colonial government in Calcutta, India. In the late 1850s and 1860s he serves there in senior-level appointments.
Trevelyan’s most enduring mark on history may be the quasi-genocidal anti-Irish racial sentiment he expresses during his term in the critical position of administrating relief to the millions of Irish peasants suffering under the Great Famine, an Gorta Mór, as Assistant Secretary to HM Treasury (1840–1859) under the Whig administration of Lord John Russell.
During the height of the famine Trevelyan deliberately drags his feet in disbursing direct government food and monetary aid to the Irish due to his strident belief in laissez-faire economics and the free hand of the market. In a letter to an Irish peer, Thomas Spring Rice, 1st Baron Monteagle of Brandon, a former Chancellor of the Exchequer, he describes the famine as an “effective mechanism for reducing surplus population” as well as “the judgement of God” and writes that “The real evil with which we have to contend is not the physical evil of the Famine, but the moral evil of the selfish, perverse and turbulent character of the people.”
Trevelyan never expresses remorse for his comments, even after the full dreadful scope of the Irish famine becomes known. His defenders claim that other factors than Trevelyan’s personal acts and beliefs are more central to the problem.
Trevelyan is referred to in the modern Irish folk song The Fields of Athenry about an Gorta Mór. For his actions, or lack thereof, during the Great Famine, he is commonly considered one of the most detested figures in Irish history, along with the likes of Oliver Cromwell.