Fenton grew up in Lincolnshire and Staffordshire, the son of Canon John Fenton, a noted biblical scholar. He was educated at Repton and Magdalen College, Oxford. He graduated with a B.A. in 1970.

Fenton acquired at school an enthusiasm for the work of W.H. Auden. At Oxford John Fuller, who happened to be writing A Reader's Guide to W.H. Auden at the time, further encouraged that enthusiasm. Auden became possibly the greatest single influence on Fenton's own work.

In his first year at university Fenton won the Newdigate Prize for his sonnet sequence Our Western Furniture. Later published by Fuller's Sycamore Press, it largely concerns the cultural collision in the 19th century between the United States and Japan. It displays in embryo many of the characteristics that define Fenton's later work: technical mastery combined with a fascination with issues that arise from the Western interaction with other cultures. Our Western Furniture was followed by Exempla, notable for its frequent use of unfamiliar words, as well as commonplace words employed in an unfamiliar manner.

His first collection, Terminal Moraine (1972) won a Gregory Award. He used the proceeds to go to East Asia, where he reported on the aftermath of the U.S. withdrawal from Vietnam, and the collapse of the Lon Nol regime in Cambodia which presaged the rise of Pol Pot. The Memory of War (1982) later secured his place as one of the finest poets of his generation.

Fenton's use of traditional form combined with comic and violent imagery to scrutinize contemporary events is evident in such poems as Out of the East and The Ballad of the Shrieking Man. Nonsense verse has long been an aspect of Fenton's output: in these poems he applies some of its metrical and linguistic verve to point up the horrors of war . . . "The lice/The meat/The burning ghats/The children buried in the butter vats/The steeple crashing through the bedroom roof/Will be your answer if you need a proof." The jaunty rhythms of Kipling are shot through with the hysteria of apocalypse.

Less insistent but just as powerful formal effects are evident in "Jerusalem", where the conflicting claims to the city are expressed in alternating and strident, mutually exclusive statements. More personal poems of love and regret such as "In Paris with You" teeter between irony and romance.

Fenton returned to London in 1976. He was political correspondent of the New Statesman, where he worked alongside Christopher Hitchens, Julian Barnes and Martin Amis. Earlier in his journalistic career, like Hitchens, he had written for Socialist Worker, the weekly paper of the British trotskyist group then known as the International Socialists.

In 1983 Fenton accompanied his friend Redmond O'Hanlon to Borneo. A description of the voyage can be found in the book "Into the Heart of Borneo".

Fenton won the Geoffrey Faber Memorial Prize in 1984 for Children in Exile: Poems 1968-1984. He was appointed Oxford Professor of Poetry in 1994, a post he held till 1999. He was awarded the Queen's Gold Medal for Poetry in 2007.

He has said, "The writing of a poem is like a child throwing stones into a mineshaft. You compose first, then you listen for the reverberation."

Fenton has been a frequent contributor to The Guardian, The Independent and The New York Review of Books. In 2007 he appeared in a list of the "100 most influential gay and lesbian people in Britain" published by The Independent on Sunday. His partner is Darryl Pinckney, the prize-winning novelist, playwright and essayist perhaps best-known for the novel High Cotton (1992).